RADAR Research and Development

Adhikari, P., Y. Hong, K. R. Douglas, D. B. Kirschbaum, J. J. Gourley, R. F. Adler, G. R. Brakenridge, 2010: A digitized global flood inventory (1998-2008): Compilation and preliminary results. J. Natural Hazards, 55, 405-422.

Adrianto, I., T. Trafalis, V. Lakshmanan, 2009: Support vector machines for spatiotemporal tornado prediction. International Journal of General Systems, 9999, .

The use of support vector machines (SVMs) for predicting the location and time of tornadoes is presented. In this paper, we extend the work by Lakshmanan et al. (Proceedings of 2005 IEEE international joint conference on neural networks (Montreal, Canada), 3, 2005a, 1642–1647) to use a set of 33 storm days and introduce some variations that improve the results. The goal is to estimate the probability of a tornado event at a particular spatial location within a given time window. We utilize a least-squares methodology to estimate shear, quality control of radar reflectivity, morphological image processing to estimate gradients, fuzzy logic to generate compact measures of tornado possibility and SVM classification to generate the final spatiotemporal probability field. On the independent test set, this method achieves a Heidke’s skill score of 0.60 and a critical success index of 0.45.

Andric, J., D. S. Zrnic, V. M. Melnikov, 2009: Polarimetric observations of precipitating and non-precipitating clouds. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, P2.12.

http://ams.confex.com/ams/34Radar/techprogram/paper_155481.htm

Andric, J., D. S. Zrnic, J. M. Straka, V. Melnikov, 2010: Enhanced ZDR signature above melting layer. Extended Abstracts, 13th Conference on Cloud Physics, Portland, OR, USA, AMS, CD-ROM, P2.89.

Available online at http://ams.confex.com/ams/13CldPhy13AtRad/techprogram/paper_171308.htm.

Bachmann, S. M., D. S. Zrnic, 2005: Spectral polarimetry for identifying and separating mixed biological scatterers. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, Amer. Meteor. Soc., P9R-5.

Bachmann, S. M., D. S. Zrnic, 2006: Spectral polarimetric VAD separates birds from insects (wind) velocities. Preprints, The 4th European Radar Conference, Barcelona, Spain, Meteocat, 96-100.

Bachmann, S. M., D. S. Zrnic, 2007: Spectral densities of polarimetric variables for retrieving winds and determining scatterer types. Preprints, The 23d Conference on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, AMS, P2.13.

Available online at http://ams.confex.com/ams/pdfpapers/115197.pdf.

Bachmann, S., V. DeBrunner, D. Zrnic, M. Yeary, 2007: Spectral analysis of polarimetric weather radar data with multiple processes in a resolution volume. Preprints, The 32nd International Conference on Acoustics, Speech, and Signal Processing, Honolulu, HI, USA, IEEE, ITT-L1.6. [Available from S. Bachmann, 120 David L. Boren Blvd., NWC Suite 4900, Norman, OK, USA, 73072.]

Bachmann, S., D. Zrnic, 2007: Adaptive technique to extract the intrinsic insects' backscatter differential phase from polarimetric spectra. Preprints, Conference on Radar Meteorology, Cairns, Australia, AMS, 11B.3.

Available online at http://ams.confex.com/ams/pdfpapers/122811.pdf.

Bachmann, S., V. DeBrunner, D. Zrnic, 2007: Detection of small aircraft with Doppler weather radar. Preprints, Statistical Signal Processing Workshop, Madison, WI, USA, IEEE, 1020. [Available from S. Bachmann, 120 David L. Boren Blvd., Suite 4900, Norman, OK, USA, 73072-7303.]

We present a method that can be performed in parallel to reflectivity estimation in weather radar and that allows one to detect small aircraft. Though small aircraft and large birds might produce comparable reflectivity signals their spectral signatures are considerably different. A small aircraft with propellers can be recognized from its spectrum via modulations produced by Doppler shifts from rotating parts. Generally such a spectrum has an elevated spectral floor compared to the spectrum of a resolution volume without an airplane. The spectral floor level is used for detection.

Bachmann, S., V. DeBrunner, D. Zrnic, M. Yeary, 2007: Adaptive technique for clutter and noise supression in weather radar exposes weak echoes over an urban area. Preprints, Statistical Signal Processing Workshop, Madison, WI, USA, IEEE, 1019. [Available from S. Bachmann, 120 David L. Boren Blvd., Suite 4900, Norman, OK, USA, 73072-7303.]

We present an adaptive spectral technique for ground clutter and noise suppression in weather radar echoes. This technique is especially good for detecting weak echoes that are either submerged in noise or masked by the residuals from ground clutter if standard techniques for clutter suppression are used. Our technique is demonstrated on two clear air cases observed with Doppler weather radar on February 22, 2007 and March 6, 2007. Adaptively suppressed ground clutter and noise allow exposure of a feature over an urban area, which we interpret as a “bird highway” between two lakes and along the river.

Bachmann, S., D. Zrnic, V. DeBrunner, 2007: Polarimetric azimuthal spectral histogram exposes types of mixed scatterers and the cause for unexpected polarimetric averages. Preprints, International Conference on Image Processing, San Antonio, TX, USA, IEEE, TP-L4.5. [Available from S. Bachmann, 120 David L. Boren Blvd., Suite 4900, Norman, OK, USA, 73072-7303.]

Echoes detected by polarimetric weather radar in clear air contain signals from air and biological scatterers. Discriminating scatterer types from a composite echo is challenging due to variability in scatterers’ quantity, azimuthal dependences of their polarimetric properties, and uneven mixing in resolution volumes. We use polarimetric spectral densities to estimate volume’s content by constructing two dimensional (2D) histograms in Doppler velocity – polarimetric variable space. Assimilation of these histograms in azimuth results in a 3D azimuthal spectral histogram (3DASH). We use transparency for small occurrences to visualize 3D signatures of the dominant content. The scatterer types have distinguishable signatures in the 3DASH due to their diverse physical shapes, scattering properties, different headings, and speeds. The 3DASH helps understand averages over the resolution volume. Further in the 3DASH one can identify intrinsic polarimetric values/functions for different types of biological scatterers, which are necessary for scatterer classification algorithms.

Bachmann, S., D. Zrnic, 2007: Spectral Density of Polarimetric Variables Separating Biological Scatterers in the VAD Display. Journal of Atmospheric and Oceanic Technology, 24, 1186-1198.

Available online at http://ams.allenpress.com/archive/1520-0426/24/7/pdf/i1520-0426-24-7-1186.pdf.

Bachmann, S., D. Zrnic, C. Curtis, 2008: Spectral identification and suppression of ground clutter contributions for phased array radar. Preprints, 24th Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, AMS, CD-ROM, 9A.4.

Available online at http://ams.confex.com/ams/pdfpapers/131493.pdf.

Bachmann, S., D. Zrnic, 2008: Three-dimentional attributes of clear-air scatterers observed with polarimetric weather radar. IEEE Geoscience Remote Sensing Letters, 5, .

Bachmann, S., D. Zrnic, 2008: Suppression of clutter residue in weather radar reveals birds’ corridors over urban area. IEEE Geoscience and Remote Sensing Letters, 5, .

Basara, J. B., P. L. Heinselman, R. Hluchan, 2010: Oklahoma City: A testbed for studying severe weather in an urban zone. Preprints, 9th Symposium on the Urban Environment, Keystone, CO, USA, Amer. Meteor. Soc., 7.2.

Officially commissioned in 2008, the Oklahoma City Micronet (OKCNET) deployed a dense network of in situ surface stations that measure atmospheric variables including air temperature, relative humidity, pressure, wind speed, wind direction, and precipitation at enhanced spatial (~3 km average station spacing) and temporal (1-minute) scales. Because Oklahoma City is embedded within a region climatologically favored for severe weather combined with the fact that the spatial dimensions of Oklahoma City are large compared to many urban areas, numerous severe weather events have been sampled by OKCNET including squall lines and tornadic supercells. When combined with additional operational and experimental observing systems in central Oklahoma (including the Phased Array Radar), Oklahoma City represents a testbed for studying (1) the impacts of severe weather across an urban area and (2) modification of severe events by the underlying urban zone. This study documents a number of specific cases including severe squall lines on 27 May 2008, 19 August 2009, and 2 April 2010 as well as tornadic supercells on 10 February 2009 and 13 May 2009.

Battaglia, A. S., S. Tanelli, S. Kobayashi, D. S. Zrnic, R. J. Hogan, 2010: Multiple-scattering in radar systems: a review. J. Quantitative Spectroscopy and Radiative Transfer, 111, 917-947.

Although extensively studied within the lidar community, the multiple scattering phenomenon has always been considered a rare curiosity by radar meteorologists. Up to few years ago its appearance has only been associated with two or three-body-scattering features (e.g. hail flares and mirror images) involving highly reflective surfaces.
Recent atmospheric research aimed at better understanding of the water cycle and the role played by clouds and precipitation in affecting the Earth’s climate has driven the deployment in space of high frequency radars, like the TRMM 13.5 GHz, the CloudSat 94 GHz, the upcoming EarthCARE 94 GHz,and the GPM dual 13-35 GHz radars. These systems have the potential of detecting the vertical distribution of hydrometeors and thus provide crucial feedbacks for radiation and climate studies. The shift towards higher frequencies increases the sensitivity to hydrometeors, improves the spatial esolution and reduces the size and weight of the radar systems. On the other hand, higher frequency radars are affected by stronger extinction, especially in presence of large precipitating particles (e.g. raindrops or hail particles), which may eventually drive the signal below the minimum detection threshold. In such circumstances the interpretation of the radar equation via the single scattering approximation may be erroneous if the radiation emitted from the radar after interacting more than once with the medium still contributes substantially to the received power. This is the case if the transport mean-free-path becomes comparable with the instrument footprint (determined by the antenna beam-width and the platform altitude).
This situation resembles to what has already been experienced in lidar observations, but with a predominance of wide- versus small-angle scattering events. At millimeter wavelengths, radiation is diffused by hydrometeors relatively isotropically compared to the visible or near infrared region where scattering is predominantly in the forward direction. A complete understanding of radiation transport modeling and data analysis methods under wide-angle multiple scattering conditions is mandatory for a correct interpretation of echoes observed by space-borne millimeter radars.
This paper reviews the status of research in this field. Different numerical techniques currently implemented to account for higher order scattering are reviewed and their weaknesses and strengths highlighted. Examples of simulated
radar backscattering profiles are provided with particular emphasis given to situations in which the multiple scattering contributions become comparable or overwhelm the single scattering signal. We show evidences of multiple scattering effects from air-borne and from the CloudSat observations, i.e. unique signatures which cannot be explained within the frame of the single scattering theory. Ideas how to identify and tackle the multiple scattering effects are discussed. Finally perspectives and suggestions for future work are outlined.
This work represents a reference-guide for studies focused at modeling the radiation transport and at interpreting data from high frequency space-borne radar systems that probe highly opaque scattering media such as thick ice clouds or precipitating clouds.

Biggerstaff, M., L. Wicker, J. Guynes, C. Ziegler, J. Straka, E. Rasmussen, A. Doggett IV, L. Carey, J. Schroeder, C. Weiss, 2005: The Shared Mobile Atmospheric Research and Teaching Radar: A collaboration to enhance research and teaching. Bulletin of the American Meteorological Society, 86, .

Biggerstaff, M. I., D. R. MacGorman, W. D. Rust, C. Ziegler, J. M. Straka, T. J. Schuur, G. Carrie, K. Kuhlman, E. Rasmussen, P. Krehbiel, W. Rison, T. Hamlin, 2005: The role of storm dynamics on cloud electrification: The 29 May 2004 Tornadic Supercell Observed During TELEX. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 15R.1.

Biggerstaff, M. I., D. W. Burgess, G. D. Carrie, E. R. Mansell, L. J. Wicker, C. L. Ziegler, 2008: Storm-Scale Sampling Strategies for the Mobile C-Band Doppler Radars during VORTEX2. Extended Abstracts, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, 5.2.

Biggerstaff, M. I., D. P. Betten, C. L. Ziegler, D. R. McGorman, L. J. Wicker, D. W. Burgess, E. R. Mansell, 2010: Rear-flank downdraft dynamics in tornadic and non-tornadic supercell thunderstorms. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, AMS, 8A.1.

Bodine, D., P. L. Heinselman, B. L. Cheong, R. Palmer, D. S. Michaud, 2008: Convection initiation and storm evolution forecasting using radar refractivity retrievals. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., 18.5.

Radar refractivity retrievals from the Oklahoma City WSR-88D (KTLX) during the spring of 2007 and 2008 have demonstrated numerous applications in forecasting convective initiation and storm evolution. Radar refractivity provides surface moisture data with high spatial and temporal resolution, and previous studies have shown that high-resolution moisture measurements are critical for convective initiation forecasts. This paper illustrates several forecasting applications of refractivity for three storm cases. On 30 April 2007, refractivity data showed that small-scale changes in moisture could be observed and used to determine where isolated thunderstorms developed. These small-scale changes in moisture eliminated convective inhibition locally and allowed convective initiation within an environment of higher convective inhibition. Moreover, refractivity data could also be used to detect boundaries before convergence lines became well defined in reflectivity. The refractivity data enables forecasters to assess the moisture changes across the boundary, which cannot be done using reflectivity data. For the 1 May 2008 case, refractivity data showed increased moisture convergence caused by the collision of a moist boundary and the dryline, which led to convective initiation. Refractivity also can detect outflow from storms, which allows forecasters to monitor its impact on surrounding storms. The 22 April 2008 case showed a storm collapsing as the outflow from another storm cutoff its inflow of warm, moist air. The outflow was not observed in the reflectivity data and was too far from a Mesonet station to be observed until the storm had collapsed. These cases illustrate the utility of radar refractivity data in convective initiation and storm evolution forecasting. Plans for expanded experiments using several radars will also be discussed.

Available online at http://ams.confex.com/ams/pdfpapers/141744.pdf.

Bodine, D., P. L. Heinselman, R. D. Palmer, D. S. Michaud, 2009: Survey of applications of radar refractivity retrievals. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P6.4.

Bodine, D., R. D. Palmer, B. L. Cheong, P. L. Heinselman, D. S. Michaud, G. Zhang, 2009: Can high-resolution surface moisture fields be retrieved in supercells?. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P6.3.

Bodine, D., P. L. Heinselman, B. L. Cheong, R. D. Palmer, D. S. Michaud, 2009: Radar refractivity applications for convection initiation forecasting and observations of the convective boundary layer.. Preprints, 25th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology., Phoenix, AZ, USA, Amer. Meteor. Soc., 14.6.

Bodine, B., P. L. Heinselman, B. L. Cheong, R. D. Palmer, D. Michaud, 2010: A case study on the impact of moisture variability on convection initiation using radar refractivity retrievals. Journal of Applied Meteorology and Climatology, 49, 1766-1778.

A case study illustrating the impact of moisture variability on convection initiation in a synoptically active environment without strong moisture gradients is presented. The preconvective environment on 30 April 2007 nearly satisfied the three conditions for convection initiation: moisture, instability, and a low-level lifting mechanism. However, a sounding analysis showed that a low-level inversion layer and high LFC would prevent convection initiation because the convective updraft velocities required to overcome the convective inhibition (CIN) were much higher than updraft velocities typically observed in convergence zones. Radar refractivity retrievals from the Twin Lakes, Oklahoma (KTLX), Weather Surveillance Radar-1988 Doppler (WSR-88D) showed a moisture pool contributing up to a 2°C increase in dewpoint temperature where the initial storm-scale convergence was observed. The analysis of the storm-relative wind field revealed that the developing storm ingested the higher moisture associated with the moisture pool. Sounding analyses showed that the moisture pool reduced or nearly eliminated CIN, lowered the LFC by about 500 m, and increased CAPE by 2.5 times. Thus, these small-scale moisture changes increased the likelihood of convection initiation within the moisture pool by creating a more favorable thermodynamic environment. The results suggest that refractivity data could improve convection initiation forecasts by assessing moisture variability at finer scales than the current observation network.

Bodine, D., R. D. Palmer, C. Ziegler, P. L. Heinselman, 2010: High-resolution radar analysis during tornadogenesis from OU-PRIME on 10 May 2010. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, Amer. Meteor. Soc., 15.4.

High-resolution polarimetric radar measurements in numerous supercells and tornadoes were obtained by the Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME) during the 10 May 2010 tornado outbreak. These observations include a supercell that produced an EF-4 tornado that developed near Moore, Oklahoma, only 10–15 km from OU-PRIME. The supercell's reflectivity appendage developed cyclonic curvature 15 min prior to the first tornado observations, coincident with an increase in low-level mesocyclone intensity and a protrusion of the rear-flank downdraft into the inflow region. Numerous cyclonic and anticyclonic flares were observed along the rear-flank downdraft (RFD) with cyclonic and anticyclonic rotation below 100 m, indicative of possible tornadoes or gustnadoes. As the RFD gust front extended further into the inflow region, vortices developed along the RFD gust front after a significant increase in near-surface convergence along the RFD gust front. In general, the vortex diameter and the spatial concentration both decreased as height increased.

To analyze the evolution of low-level rotation during tornadogenesis, single-radar approximations of vorticity and convergence in the RFD region are computed. Vorticity and convergence are computed using radial velocity differences between two gates over a fixed number of gates. The possible role of vorticity along the RFD gust front in tornadogenesis will be discussed, along with other vorticity sources identified in the analysis.

Available online at http://ams.confex.com/ams/25SLS/techprogram/paper_175834.htm.

Boodoo, S., D. Hudak, M. Leduc, A. Ryzhkov, N. Donaldson, D. Hassan, 2009: Hail detection with a C-band dual-polarization radar in the Canadian Great Lakes region. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, 10A.5.

Available online at http://ams.confex.com/ams/pdfpapers/156032.pdf.

Borowska, L., A. Ryzhkov, D. Zrnic, P. Zhang, J. Gu, P. Neilley, M. Knight, R. Palmer, B. Cheong, A. Battaglia, C. Simmer, 2009: Attenuation of radar signal in melting hail at C band. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, P2.7.

Available online at http://ams.confex.com/ams/pdfpapers/155402.pdf.

Borowska, L., A. Ryzhkov, D. Zrnic, C. Simmer, R. Palmer, 2011: Attenuation and differential attenuation of 5-cm-wavelength radiation in melting hail. Journal of Applied Meteorology and Climatology, 50, 59-76.

Presented are quantitative estimates of specific attenuation and specific differential attenuation of 5-cmwavelength radiation (C band) obtained by comparison with measurements at 10-cm wavelength (S band), which are much less affected by attenuation. The data originated from two almost-collocated radars in central Oklahoma. To avoid biases in estimates, the slopes with respect to range of differences in reflectivities and differential reflectivities are assumed to represent the specific attenuations. Observations on a day with no reports of hail on the ground and on a day with large hail are contrasted. A simple one-dimensional model of melting hail is used to qualify these observations. Examples of volumetric fields of the polarimetric variables obtained at the two wavelengths are presented to illustrate that much can be learned about size, orientation, and phase of hydrometeors over volumes that play a role in precipitation formation.

Borowska, L., D. Zrnic, A. Ryzhkov, P. Zhang, 2011: Polarimetric Estimates of a 1-Month Accumulation of Light Rain with a 3-cm Wavelength Radar. JOURNAL OF HYDROMETEOROLOGY, 12, 1024-1039.

The authors evaluate rainfall estimates from the new polarimetric X-band radar at Bonn, Germany, for a
period between mid-November and the end of December 2009 by comparison with rain gauges. The emphasis
is on slightly more than 1-month accumulations over areas minimally affected by beam blockage. The rain
regime was characterized by reflectivities mainly below 45 dBZ, maximum observed rain rates of 47 mm h21,
a mean rain rate of 0.1 mm h21, and brightband altitudes between 0.6 and 2.4 km above the ground. Both the
reflectivity factor and the specific differential phase are used to obtain the rain rates. The accuracy of rain total
estimates is evaluated from the statistics of the differences between radar and rain gauge measurements.
Polarimetry provides improvement in the statistics of reflectivity-based measurements by reducing the bias
and RMS errors from 225% to 7% and from 33% to 17%, respectively. Essential to this improvement is
separation of the data into those attributed to pure rain, those from the bright band, and those due to nonmeteorological
scatterers. A type-specific (rain or wet snow) relation is applied to obtain the rain rate by
matching on the average the contribution by wet snow to the radar-measured rainfall below the bright band.
The measurement of rain using specific differential phase is the most robust and can be applied to the very low
rain rates and still produce credible accumulation estimates characterized with a standard deviation of 11%
but a bias of 225%. A composite estimator is also tested and discussed.

Borowska, L., D. Zrnic, 2012: Use of Ground Clutter to Monitor Polarimetric Radar Calibration. Journal of Atmospheric and Oceanic Technology, 29, 159-176.

It is suggested that urban ground clutter can have a role in monitoring calibration of reflectivity factor ZH
and differential reflectivity ZDR on polarimetric radars. The median and average values of these variables are
considered. Analysis of data from 1 month of cold season in Germany (X-band radar) and 3.5 hot days in
Oklahoma (S-band radar) is presented. In the presence of up to moderate rain or snow a reflectivity threshold
suffices for separating significant clutter from precipitation observed with an X-band radar. The same
threshold was suitable on observations with an S-band radar in Oklahoma because heavy precipitation was
not present. The tests suggest the scheme is worthy considering for operational monitoring of ZH as its median
values at both locations were within the quantization interval of 0.5 dB. Environmental factors that can
influence reflectivities from clutter are examined. The effects on ZDR can be significant. These are quantified
in the data and possible uses for calibration and monitoring radar status are indicated.

Brandes, E. A., T. J. Schuur, A. V. Ryzhkov, G. Zhang, K. Ikeda, 2005: Rain Microphysics Retrieval with a Polarimetric WSR-88D. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, 9R.2.

Brandes, E. A., K. Ikeda, K. L. Elmore, A. V. Ryzhkov, T. J. Schuur, 2006: Aviation weather hazard detection with polarimetric radar. Preprints, 12th Conference on Aviation, Range, and Aerospace Meteorology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, 6.1.

Brooks, H. E., P. T. Marsh, A. M. Kowaleski, P. Groenemeijer, T. E. Thompson, C. S. Schwartz, C. M. Shafer, A. Kolodziej, N. Dahl, D. Buckey, 2011: Evaluation of European Storm Forecast Experiment (ESTOFEX) forecasts. Atmospheric Research, 100, 538-546.

Three years of forecasts of lightning and severe thunderstorms from the European Storm Forecast Experiment (ESTOFEX) have been evaluated. The forecasts exhibit higher quality in summer than in winter and there is some evidence that they have improved over the course of the evaluation. Five individual forecasters made the majority of the forecasts and differences in their forecasts are on the order of the overall variability of the forecast quality. As a result, the forecasts appear to come from a single unit, rather than from a group of individuals.
The graphical description of the probability of detection and frequency of hits recently developed by Roebber is a valuable tool for displaying the time series of lightning forecast performance. It also appears that, even though they are not intended for that purpose, using the lightning forecasts as a low-end forecast of severe thunderstorms is potentially useful for decision makers.

Available online at http://www.nssl.noaa.gov/users/brooks/public_html/papers/brooksetalestofex2011.pdf.

Brotzge, J., D. Westbrook, K. Brewster, K. Hondl, M. Zink, 2005: The Meteorological Command and Control Structure of a Dynamic, Collaborative, Automated Radar Network.. Preprints, 21st International Conf. on Interactive Information Processing Systems (IIPS) for Meteor., Ocean., and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 19.15.

Brotzge, J., K. Brewster, V. Chandrasekar, B. Philips, S. Hill, K. Hondl, B. Johnson, E. Lyons, D. McLaughlin, D. Westbrook, 2007: CASA IP1: Network Operations and Initial Data.. Preprints, 23rd International Conf. on Interactive Information Processing Systems (IIPS) for Meteor., Ocean., and Hydrology, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 8A.6.

Brotzge, J., K. Hondl, B. Philips, L. Lemon, E. Bass, D. Rude, D. Andra, 2010: Evaluation of Distributed Collaborative Adaptive Sensing for Detection of Low-Level Circulations and Implications for Severe Weather Warning Operations. Weather and Forecasting, 25, 173-189.

The Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) is a multiyear engineering research center established by the National Science Foundation for the development of small, inexpensive, low-power radars designed to improve the scanning of the lowest levels (<3 km AGL) of the atmosphere. Instead of sensing autonomously, CASA radars are designed to operate as a network, collectively adapting to the changing needs of end users and the environment; this network approach to scanning is known as distributed collaborative adaptive sensing (DCAS). DCAS optimizes the low-level volume coverage scanning and maximizes the utility of each scanning cycle. A test bed of four prototype CASA radars was deployed in southwestern Oklahoma in 2006 and operated continuously while in DCAS mode from March through June of 2007.

This paper analyzes three convective events observed during April–May 2007, during CASA’s intense operation period (IOP), with a special focus on evaluating the benefits and weaknesses of CASA radar system deployment and DCAS scanning strategy of detecting and tracking low-level circulations. Data collected from nearby Weather Surveillance Radar-1988 Doppler (WSR-88D) and CASA radars are compared for mesoscyclones, misocyclones, and low-level vortices. Initial results indicate that the dense, overlapping coverage at low levels provided by the CASA radars and the high temporal (60 s) resolution provided by DCAS give forecasters more detailed feature continuity and tracking. Moreover, the CASA system is able to resolve a whole class of circulations—misocyclones—far better than the WSR-88Ds. In fact, many of these are probably missed completely by the WSR-88D. The impacts of this increased detail on severe weather warnings are under investigation. Ongoing efforts include enhancing the DCAS data quality and scanning strategy, improving the DCAS data visualization, and developing a robust infrastructure to better support forecast and warning operations.

Brown, R. A., B. A. Flickinger, E. Forren, D. M. Schultz, D. Sirmans, P. L. Spencer, V. T. Wood, C. L. Ziegler, 2005: Improved detection of severe storms using experimental fine-resolution WSR-88D measurements. Weather and Forecasting, 20, 3-14.

NSSL Outstanding Scientific Paper Award

Doppler velocity and reflectivity measurements from WSR-88D (Weather Surveillance Radar - 1988 Doppler) radars provide important input to forecasters as they prepare to issue short-term severe storm and tornado warnings. Current-resolution data collected by the radars have an azimuthal spacing of 1.0° and range spacing of 1.0 km for reflectivity and 0.25 km for Doppler velocity and spectrum width. To test the feasibility of improving data resolution, National Severe Storms Laboratory's test-bed WSR-88D (KOUN) collected data in severe thunderstorms using 0.5° azimuthal spacing and 0.25 km range spacing,resulting in eight times the resolution for reflectivity and twice the resolution for Doppler velocity and spectrum width. Displays of current-resolution WSR-88D Doppler velocity and reflectivity signatures in severe storms were compared with displays showing finer-resolution signatures. At all ranges, fine-resolution data provided better depiction of severe storm characteristics. Eighty-five percent of mean rotational velocities derived from fine-resolution mesocyclone signatures were stronger than velocities derived from current-resolution signatures. Likewise, about 85% of Doppler velocity differences across tornado and tornadic vortex signatures were stronger than values derived from current-resolution data. In addition, low-altitude boundaries were more readily detected using fine-resolution reflectivity data. At ranges greater than 100 km, fine-resolution reflectivity displays revealed severe storm signatures, such as bounded weak echo regions and hook echoes, which were not readily apparent on current-resolution displays. Thus, the primary advantage of fine-resolution measurements over current-resolution measurements is the ability to detect stronger reflectivity and Doppler velocity signatures at greater ranges from a WSR-88D.

Brown, R. A., R. M. Steadham, B. A. Flickinger, R. R. Lee, D. Sirmans, V. T. Wood, 2005: New WSR-88D volume coverage pattern 12: Results of field tests. Weather and Forecasting, 20, 385-393.

For the first time since the installation of the national network of WSR-88D radars, a new scanning strategy -- Volume Coverage Pattern 12 -- has been added to the suite of scanning strategies. VCP 12 is a faster version of VCP 11 and has denser vertical sampling at lower elevation angles. This note discusses results of field tests in Oklahoma and Mississippi during 2001 - 2003 that led to the decision to implement VCP 12. Output from meteorological algorithms for a test-bed radar using an experimental VCP were compared with output for a nearby operational WSR-88D using VCP 11 or 21. These comparisons were made for severe storms that were at comparable distances from both radars. Findings indicate that denser vertical sampling at lower elevation angles leads to earlier and longer algorithm identifications of storm cells and mesocyclones, especially those more distant from a radar.

Brown, R. A., J. M. Lewis, 2005: Path to NEXRAD: Doppler radar development at the National Severe Storms Laboratory. Bulletin of the American Meteorological Society, 86, 1459-1470.

In this historical paper, we trace the scientific- and engineering-based steps at the National Severe Storms Laboratory (NSSL) and in the larger weather radar community that led to the development of NSSL's first 10-cm wavelength pulsed Doppler radar. This radar was the prototype for the current NEXRAD (NEXt generation weather RADar) or WSR-88D (Weather Surveillance Radar-1988 Doppler) Network.

We track events, both political and scientific, that led to the establishment of NSSL in 1964. The vision of NSSL's first director, Edwin Kessler, is reconstructed through access to historical documents and oral history. This vision included the development of Doppler radar where research was to be meshed with the operational needs of the U.S. Weather Bureau and its successor the National Weather Service.

Realization of the vision came through steps that were often fitful, where complications arose due to personnel concerns, and where there were always financial concerns. The historical research indicates that: (1) the engineering prowess and mentorship of Roger Lhermitte was at the heart of Doppler radar development at NSSL; (2) key decisions by Kessler in the wake of Lhermitte's sudden departure in 1967 proved crucial to the ultimate success of the project; (3) research results indicated that Doppler velocity signatures of mesocyclones are a precursor of damaging thunderstorms and tornadoes; and (4) results from field testing of the Doppler-derived products during the 1977-1979 Joint Doppler Operational Project -- especially the noticeable increase in the verification of tornado warnings and an associated marked decrease in false alarms -- led to the government decision to establish the NEXRAD network.

Brown, R. A., J. M. Kurdzo, P. L. Heinselman, 2009: Progress report on evolutionary characteristics of a tornadic supercell thunderstorm: Comparisons of 1.0–min phased array radar and 4.2–min WSR–88D measurements. Preprints, 25th International Conference on Interactive Information and Processing Systems, Phoenix, AZ, USA, American Meteorological Society, 9B.3.

Brown, A., S. Van Cooten, K. Howard, K. Willingham, J. Zhang, C. Langston, 2011: Analysis of National Mosaic and Multi-sensor Quantitative Precipitation Estimates during warm season rainfall events in Oklahoma. Preprints, Hydrologic Prediction and Verification for Water and Energy Resources and Other Applications- 25th Conference on Hydrology, Seattle, WA, USA, American Meteorological Society, 377.

Accurate estimates of areal rainfall are critical for water management. Inaccuracies in quantitative precipitation estimates (QPE) can lead to inaccurate stream flow simulations, which provide erroneous information to forecasters responsible for flood and flash flood warning products. The National Mosaic and Multi-sensor QPE (NMQ), developed by the National Severe Storms Laboratory, is a tool used to increase the accuracy of rainfall estimates. The NMQ integrates raw radar, rain gauge, and RUC model data to produce gridded precipitation estimates.

May is Oklahoma's climatological rainiest month and presents interesting challenges for water resource monitoring and management. Thus, heavy rainfall events in Oklahoma during May are examined using vertical profiles of reflectivity (VPR) created through the NMQ system, in conjunction with upper-air, RUC model, and surface rain gauge data. Particular attention is paid to the environmental conditions necessary to produce excessive rainfall rates estimated by the NMQ.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper179837.html.

Bruning, E., W. D. Rust, D. MacGorman, T. Schuur, J. Straka, P. Krehbiel, W. Rison, T. Hamlin, 2005: Polarimetric radar and electrical structure of a multicell storm. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P14R.9.

Bruning, E. C., W. D. Rust, T. J. Schuur, D. R. MacGorman, P. R. Krehbiel, W. Rison, 2007: Electrical and Polarimetric Radar Observations of a Multicell Storm in TELEX. Monthly Weather Review, 135, 2525-2544.

On 28-29 June 2004 a multicellular thunderstorm west of Oklahoma City was probed as part of the Thunderstorm Electrification and Lightning Experiment (TELEX) field program. This study makes use of radar observations from the KOUN polarimetric WSR-88D, threedimensional lightning mapping data from the Oklahoma Lightning Mapping Array (LMA), and balloon-borne vector electric field meter (EFM) measurements. The storm had a low flash rate (30 flashes in 40 min). Four charge regions were inferred from a combination of LMA and EFM data. Lower positive charge near 4 km and mid-level negative charge from 4.5–6 km MSL (0 to -6.5°C) were generated in and adjacent to a vigorous updraft pulse. Further mid-level negative charge from 4.5–6 km MSL and upper positive charge from 6–8 km (-6.5 to -19°C) were generated later in quantity sufficient to initiate lightning as the updraft decayed. A negative screening layer was present near storm top (8.5 km MSL, -25°C). Initial lightning flashes were between lower positive and mid-level negative charge and started occurring shortly after a cell began lofting hydrometeors into the mixed phase region, where graupel was formed. A leader from the storm's first flash avoided a region where polarimetric radar suggested wet growth and the resultant absence of non-inductive charging of those hydrometeors. Initiation locations of later flashes that propagated into upper positive charge tracked the descending location of a polarimetric signature of graupel. As the storm decayed, electric fields greater than 160 kV m-1 exceeded the minimum threshold for lightning initiation suggested by the hypothesized runaway breakdown process at 5.5 km MSL, but lightning did not occur. The small spatial extent (≈100 m) of the large electric field may not have been sufficient to allow runaway breakdown to fully develop and initiate lightning.

Bruning, E. C., W. D. Rust, D. R. MacGorman, T. J. Schuur, P. R. Krehbiel, W. Rison, 2007: Temporal and Spatial Structure of Storm Charge and Kinematics in the 26 May 2004 Supercell Storm During TELEX. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, International Commission on Atmospheric Electricity, 229-232. [Available from W. D. Rust, National Severe Storms Laboratory, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Bruning, E. C., W. D. Rust, D. R. MacGorman, M. I. Biggerstaff, T. J. Schuur, 2010: Formation of Charge Structures in a Supercell. Monthly Weather Review, 138, 3740-3761.

Lightning mapping, electric field, and radar data from the 26 May 2004 supercell in central Oklahoma are used to examine the storm’s charge structure. An initial arc-shaped maximum in lightning activity on the right flank of the storm’s bounded weak echo region was composed of an elevated normal polarity tripole in the region of precipitation lofted above the storm’s weak echo region. Later in the storm, two charge structures were associated with precipitation that reached the ground. To the left of the weak echo region, six charge regions were inferred, with positive charge carried on hail at the bottom of the stack. Farther forward in the storm’s precipitation region, four charge regions were inferred, with negative charge at the bottom of the stack. There were different charge structures in adjacent regions of the storm at the same time, and regions of opposite polarity charge were horizontally adjacent at the same altitude. Flashes ccasionally lowered positive charge to ground from the forward charge region. A conceptual model is presented that ties charge structure in different regions of the storm to storm structure inferred from radar reflectivity.

Brunner, J. C., S. A. Ackerman, A. S. Bachmeier, R. M. Rabin, 2006: A quantitative analysis of the enhanced-V signature in relation to severe weather. Proc. Symposium on the Challenges of Severe Convective Storms; 86th AMS Annual meeting., Atlanta, GA, USA, AMS, P1.4. [Available from Jason Brunner, SSEC, 1225 W. Dayton, Madison, WI, USA, 53706.]

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_102728.htm.

Brunner, J. C., A. S. Bachmeier, R. M. Rabin, S. A. Ackerman, 2006: A quantitative analysis of the enhanced-V feature. Preprints, 14th Conference on Satellite Meteorology and Oceanography: 86th AMS Annual Meeting. Atlanta, GA. 29 Jan.-02 Feb. 2006., Atlanta, GA, USA, AMS, P3.16. [Available from Jason Brunner, SSEC, 1225 W. Dayton St., Madison, WI, USA, 53706.]

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_102719.htm.

Brunner, J. C., S. A. Ackerman, A. S. Bachmeier, R. M. Rabin, 2007: A Quantitative Analysis of the Enhanced-V Feature in Relation to Severe Weather. Weather and Forecasting, 22, 853-872.

Buban, M. S., C. L. Ziegler, E. N. Rasmussen, Y. P. Richardson, 2007: The Dryline on 22 May 2002 during IHOP: Ground-Radar and In Situ Data Analyses of the Dryline and Boundary Layer Evolution. Monthly Weather Review, 135, 2473-2505.

On the afternoon and evening of 22 May 2002, high-resolution observations of the boundary layer (BL) and a dryline were obtained in the eastern Oklahoma and Texas panhandles during the International H2O Project. Using overdetermined multiple-Doppler radar syntheses in concert with a Lagrangian analysis of water vapor and temperature fields, the 3D kinematic and thermodynamic structure of the dryline and surrounding BL have been analyzed over a nearly 2-h period. The dryline is resolved as a strong (2–4 g/kg/km) gradient of water vapor mixing ratio that resides in a nearly north–south-oriented zone of convergence. Maintained through frontogenesis, the dryline is also located within a gradient of virtual potential temperature, which induces a persistent, solenoidally forced secondary circulation. Initially quasi-stationary, the dryline retrogrades to the west during early evening and displays complicated substructures including small wavelike perturbations that travel from south to north at nearly the speed of the mean BL flow. A second, minor dryline has similar characteristics to the first, but has weaker gradients and circulations. The BL adjacent to the dryline exhibits complicated structures, consisting of combinations of open cells, horizontal convective rolls, and transverse rolls. Strong convergence and vertical motion at the dryline act to lift moisture, and high-based cumulus clouds are observed in the analysis domain. Although the top of the analysis domain is below the lifted condensation level height, vertical extrapolation of the moisture fields generally agrees with cloud locations. Mesoscale vortices that move along the dryline induce a transient eastward dryline motion due to the eastward advection of dry air following misocyclone passage. Refractivity-based moisture and differential reflectivity analyses are used to help interpret the Lagrangian analyses.

Buban, M., C. L. Ziegler, E. N. Rasmussen, Y. Richardson, 2005: The structure and evolution of the dryline and surrounding boundary layer on 22 May 2002 during IHOP. Preprints, 11th Conference on Mesoscale Processes, Albuquerque, NM, USA, AMS, J6J.3.

Buban, M., C. Ziegler, Y. Richardson, 2008: Numerical simulations of the dryline and surrounding boundary layer on 22 May 2002 during IHOP. Extended Abstracts, 24th Conference on Severe Local Storms, Savannah, GA, USA, AMS, 18.4.

On the afternoon and evening of 22 May 2002, high-resolution data of the dryline and surrounding boundary layer (BL) were collected in the Oklahoma and Texas panhandles as part of the International H2O Project. Using over-determined multiple Doppler radar syntheses in concert with an innovative Lagrangian analysis technique, the 3-D kinematic and thermodynamic structure of the dryline and surrounding BL have been obtained over nearly a 2-hour period. A past study utilizing these analysis tools has delineated the 22 May dryline as a strong gradient of water vapor mixing ratio embedded in a zone of multi-Doppler radar-derived convergence. Misocyclones are observed to propagate from south to north along the dryline. The BL on both sides of the dryline exhibits complicated structures such as horizontal convective rolls, transverse rolls, and open convective cells.

In the present study, the time-varying radar and Lagrangian analyses have been used as initial and time-dependent lateral inflow boundary conditions to run high-resolution simulations of the dryline and BL. Simulations are conducted with the COllaborative Model for Multiscale Atmospheric Simulation (COMMAS), a 3-dimensional non-hydrostatic community cloud model which includes both short- and long-wave radiation, a force-restore surface physics parameterization, and a cloud microphysics parameterization. The simulations reproduce a nearly north-south oriented dryline with horizontal moisture and temperature gradients similar to observed values, as well as misocyclones, horizontal convective rolls, transverse rolls, and open convective cells. These simulated BL features are similar to analogous structures manifested in the observations and the Lagrangian analyses, although the modeled features are typically of higher spatial and temporal resolutions and may have larger amplitudes than the equivalent observed features. The simulated BL features are internally consistent with the model dynamics, with the high spatial and temporal resolution potentially permitting a better understanding of their evolution processes.

A feature of special interest are the misocyclones which develop and propagate northward along the dryline. Apparently forced in the simulations via longer wavelength undulations in the momentum and thermodynamic fields that are introduced at the lateral inflow boundaries, these perturbations collapse in scale and amplify into intense misovortices as they move downstream. The misocyclones act to modulate the moisture fields along the dryline, bringing larger moisture values westward ahead of and drier air eastward behind the misocyclone relative to its motion. The vertical motion within the deeper moist layer north of the misocyclone enhances simulated cumulus formation along and north of the axis of rotation.

The model simulations are compared to observations to qualitatively evaluate the strengths and weaknesses of the Lagrangian analyses. Aspects of the dryline circulation and other BL features are discussed along with their potential role in the convection initiation process.

Burgess, D. W., E. Mansell, C. Schwarz, B. Allen, 2010: Tornado and tornadogenesis events seen by the NOXP x-band, dual-polarization radar during VORTEX2 2010. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, AMS, 5.2.

Burnett, M. L., T. M. Smith, V. Lakshmanan, 2010: Improvements on Cluster Identification and Tracking in a New Circulation Detection Algorithm. Extended Abstracts, 26th Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, AMS, 53.

Circulation detection algorithms such as the Mesocyclone Detection Algorithm (MDA) and the Tornado Detection Algorithm (TDA) have been used by National Weather Service forecasters to aid with warning decision-making since the mid-1990s. However, the MDA and TDA are often plagued with misidentified circulations and poor tracking which limit their use as an operational tool. Because of ever-increasing data flow rates from radar upgrades (e.g. WSR-88D “super-resolution”), new technologies (e.g. Phased Array Radar), and the need to quickly analyze circulation signatures in the immense historical WSR-88D data set, NSSL is developing an improved algorithm to identify, diagnose, and track both mesocyclone and tornado size circulations. The algorithm operates on a field of “azimuthal shear”, which is the rotational derivative of the Doppler radial velocity field. “Clusters” of high azimuthal shear values in both low level (0-3 km above the surface) and mid level (3-7 km above the surface) layers of the storm are identified in the radar data. The clustering and tracking methods were developed on relatively smooth reflectivity fields, but are now being applied to a much noisier azimuthal shear field. This project compares multiple methods of cluster identification and tracking to determine which is best.

Available online at http://ams.confex.com/ams/90annual/techprogram/paper_162496.htm.

Cao, Q., G. Zhang, T. J. Schuur, A. V. Ryzhkov, E. Brandes, K. Ikeda, 2006: Characterization of rain microphysics and polarimetric signatures based on disdrometer and radar observations. Preprints, IGARRS 2006, Denver, CO, USA, Institute of Electrical and Electronics Engineers, 02_11A05.

Cao, Q., G. Zhang, E. Brandes, T. Schuur, A. Ryzhkov, K. Ikeda, 2008: Analysis of video disdrometer and polarimetric radar data to characterize rain microphysics in Oklahoma. Journal of Applied Meteorology and Climatology, 47, 2238-2255.

Cao, Q., G. Zhang, E. A. Brandes, T. J. Schuur, 2010: Polarimetric radar rain estimation through retrieval of drop size distribution using Bayesian approach.. Journal of Applied Meteorology and Climatology, 49, 973-990.

This study proposes a Bayesian approach to retrieve raindrop size distributions (DSDs) and to estimate rainfall rates from radar reflectivity in horizontal polarization ZH and differential reflectivity ZDR. With this approach, the authors apply a constrained-gamma model with an updated constraining relation to retrieve DSD parameters. Long-term DSD measurements made in central Oklahoma by the two-dimensional video disdrometer (2DVD) are first used to construct a prior probability density function (PDF) of DSD parameters, which are estimated using truncated gamma fits to the second, fourth, and sixth moments of the distributions. The forward models of ZH and ZDR are then developed based on a T-matrix calculation of raindrop backscattering amplitude with the assumption of drop shape. The conditional PDF of ZH and ZDR is assumed to be a bivariate normal function with appropriate standard deviations. The Bayesian algorithm has a good performance according to the evaluation with simulated ZH and ZDR. The algorithm is also tested on S-band radar data for a mesoscale convective system that passed over central Oklahoma on 13 May 2005. Retrievals of rainfall rates and 1-h rain accumulations are compared with in situ measurements from one 2DVD and six Oklahoma Mesonet rain gauges, located at distances of 28–54 km from Norman, Oklahoma. Results show that the rain estimates from the retrieval agree well with the in situ measurements, demonstrating the validity of the Bayesian retrieval algorithm.

Chang, P. L., J. D. Jou, J. Zhang, 2009: An algorithm for tracking eyes of tropical cyclones. Weather and Forecasting, 24, 245-261.

Chang, P. L., P. F. Lin, J. D. Jou, J. Zhang, 2009: An application of reflectivity climatology in constructing radar hybrid scan over complex terrains. Journal of Atmospheric and Oceanic Technology, 26, 1315-1327.

Cheong, B. L., R. D. Palmer, T. Y. Yu, C. Curtis, 2005: Refractivity Measurements from Ground Clutter Using the National Weather Radar Testbed Phased Array Radar. Proc. 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P1R.10.

Cheong, B., R. Palmer, C. Curtis, K. Hondl, P. Heinselman, D. Zrnic, D. Forsyth, R. Murnan, R. Reed, R. Vogt, M. Foster, 2007: Real-time implementation of refractivity retrieval: Partnership between the University of Oklahoma, National Severe Storms Laboratory, and the Radar Operations Center. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, American Meteorological Society, CD-ROM, P8B.8.

High-resolution, near-surface refractivity measurements have the potential of becoming an important tool for operational forecasting and general scientific studies. Access to measured refractivity fields with high spatial and temporal resolution near the surface opens a new paradigm for understanding the convective processes within the boundary layer. It has been shown via advanced physical models that surface refractivity plays an important role in con vective processes and, therefore, is expected to be valuable for forecasting of the initiation and intensity of convective precipitation. For this project, the refractivity field is retrieved remotely using S-band radars by measuring the returned phase from ground clutter. Pioneering work of Fabry et. al. [J. Atmos. Oceanic Technol., 14, 978-987, 1997] has demonstrated the usefulness of this technique. By adopting this refractivity retrieval concept, an independent real-time software platform has been developed. The software was written with a modular design for portability and will be tested during the spring 2007 storm season on two radars in Oklahoma. Both the National Weather Radar Testbed (Phased Array), maintained by the National Severe Storm Laboratory (NSSL), and the WSR-88D weather radar near Oklahoma City (KTLX), supported by the Radar Operations Center (ROC), will be used for this study. Using the raw Level-I time series data from the radars, the modular software platform will be used to process the data in real-time for refractivity fields, which will be sent to the Norman Weather Forecast Office (WFO) for evaluation. Working closely with the WFO forecasters, qualitative assessment procedures will be followed to evaluate the usefulness of the refractivity fields for operational forecasting.

Cheong, B. L., R. D. Palmer, C. D. Curtis, T. Y. Yu, D. S. Zrnic, D. Forsyth, 2007: Refractivity measurements from ground clutter using the National Weather Radar Testbed phased array Radar. Preprints, The 23rd Conference on Interactive Information Processing Systems(IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 8A.3A.

Cheong, B. L., R. D. Palmer, C. D. Curtis, T. Y. Yu, D. S. Zrnic, D. Forsyth, 2008: Refractivity retrieval using the phased-array radar: First results and potential for multimission operation. IEEE Trans. Geosci. Remote Sens., 46, 2527-2537.

Cheong, B. L., R. Palmer, S. Torres, 2011: Automatic wind turbine detection using level-II data. Extended Abstracts, 2nd Conf. on Weather, Climate, and the New Energy Economy, Seattle, WA, USA, Amer. Meteor. Soc., CD-ROM, 808.

Wind power is considered a “green” form of electricity production as it is renewable and ecologically friendly. While there are countless benefits from its growth, the negative impacts should not be neglected. One such impact is the contamination induced on radar signals, which are essential for weather forecasting and warning decisions for public safety. In this work, an algorithm for automatic wind turbine detection from Level-II moment data, i.e., reflectivity, Doppler velocity and spectrum width, was developed. The algorithm utilizes a series of consecutive moment maps and a Fuzzy-logic inference system for detection. The impetus for this project is to design and realize a detection technique that requires minimal modifications to the existing WSR-88D infrastructure. That is, we began with a restriction of only utilizing Level-II data. Most of the time, a wind farm within the radar domain can be visually identified from Level-II data by inspecting several consecutive images and looking for stationary features. Most weather features on the radar maps advect and deform but features from ground targets, including wind turbine clutter, would remain at the same locations and that is how they provide us with visual queues for identification. Current operational ground clutter filter, i.e., GMAP (Gaussian Model Adaptive Processing), does not completely filter out wind turbine clutter simply because it is not designed to do so. Even other clutter filters are meant for filtering targets at near-zero velocity. Residual signals from the wind turbine clutter through these ground clutter filters still contaminate meteorological data and it is our primary goal of this work to design, implement and test of an automatic detection technique to identify the residual wind turbine clutter signals using Level-II data. We focus on areas where GMAP has been applied, i.e., areas where the CMD (Clutter Mitigation Decision) flag has been marked. Understanding how human visual systems identify these residual signals of wind turbine clutter from the GMAP, it was believed that by processing several consecutive images at a time, a similar detection scheme, which is also suitable for computer implementation, could be realized. A fundamental algorithm has been developed, which utilizes the CMD flag, six running-temporal textures, and numerical statistics of the moment values, and a fuzzy-logic inference system for the detection. In the paper, a detailed description of the algorithm and some examples from several WSR-88D radars, e.g., KDDC, KDYX, KBUF, etc., will be presented. Of course, moment dataset with the highest temporal resolution of 5-minute would limit the performance of the algorithm and they will be discussed. A more thorough system evaluation is currently underway and the results will be reported.

Chilson, P. B., R. D. Palmer, M. Teshiba, A. V. Ryzhkov, T. J. Schuur, 2006: Combined observations of precipitation using wind profilers and polarimetric weather radars. Preprints, 7th International Symposium on Tropospheric Profiling Needs and Technologies, Boulder, CO, USA, National Center for Atmospheric Research, 6.1-O.

Chilson, P. B., G. Zhang, T. J. Schuur, A. V. Ryzhkov, L. Kanofsky, M. Teshiba, Q. Cao, M. Van Every, 2007: Coordinated in-situ and remote sensing precipitation measurements at the Kessler Farm Field Laboratory in central Oklahoma. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, American Meteorological Society, P8A.4.

Chilson, P. B., M. Morris, A. Ryzhkov, T. Schuur, M. Teshiba, R. D. Palmer, 2009: Combined Wind profiler and Polarimetric Weather Radar Observations of Squall Lines. Proc. MST12 Radar Workshop, London, Canada, URSI, T5.16.

Cintineo, J. L., T. M. Smith, V. Lakshmanan, K. L. Ortega, 2009: A real-time automated method to determine forecast confidence associated with tornado warnings. Extended Abstracts, 25th Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, American Meteorological Society, 4B.1.

This presentation describes the use of severe weather products derived from the coterminous United States (CONUS) radar network and model analysis fields to determine the confidence-level of National Weather Service-issued tornado warnings. Severe weather attributes such as low-level shear, reflectivity at -20C and the size of the convective core were extracted (within the geographic and temporal extent of the warning polygons) from the real-time grids produced by the Warning Decision Support System -- Integrated Information (WDSS-II). The initial values of these severe weather parameters at the time the warning was issued were used to determine the conditional probability that a tornado would occur within the spatial and temporal bounds of the warning. The results are based on NWS tornado warnings from May and July of 2008, and also based on verification data from the Storm Prediction Center's storm data, which were preliminary at the time the analysis was performed. Conditional probabilities are shown from two products: 0-2km azimuthal shear, and vertically integrated liquid. Once a warning is issued, it is possible to use this conditional probability to objectively assign a confidence value with the warning in real-time.

Available online at http://ams.confex.com/ams/89annual/techprogram/paper_150730.htm.

Cintineo, J. L., T. M. Smith, V. Lakshmanan, S. Ansari, 2011: An automated system for processing the Multi-Year Reanalysis Of Remotely-Sensed Storms (MYRORSS). Extended Abstracts, 27th Conference on Interactive Information Processing Systems (IIPS), Seattle, WA, USA, AMS, J9.3.

The Multi-Year Reanalysis Of Remotely-Sensed Storms (MYRORSS) is a cooperative endeavor between the National Oceanic and Atmospheric Administration's (NOAA) National Severe Storms Laboratory (NSSL) and the National Climatic Data Center (NCDC) to reconstruct and evaluate numerical model output and radar products derived from 15 years of WSR-88D data over the coterminous U.S. (CONUS). The end result of this research will be a rich dataset with a diverse range of applications, including severe weather diagnosis and climatological information. An automated system has been developed by the NSSL for processing level-II radar data provided by NCDC. The system operates in a multiple-machine framework, with an already existing network of computers. This procedure maximizes processing power on each machine and utilizes idle time from other users' computers. The Warning Decision Support System – Integrated Information (WDSS-II) suite of programs are used to process and quality-control the data. The system operates in three main phases. The first phase is single-radar processing from each individual radar in the CONUS, which includes quality-control of the level-II data and creation of velocity-derived products. The second phase creates blended 3D reflectivity fields as well as 2D fields derived from radial velocity data. The third phase runs post-processing algorithms on merged meteorological fields and ingested near storm environment data provided by the Rapid Update Cycle model (RUC). Applications for this work are discussed and preliminary results are shown for one year of CONUS NEXRAD and RUC data.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper182332.html.

Clark, A. J., S. J. Weiss, J. S. Kain, I. L. Jirak, M. C. Coniglio, C. J. Melick, C. Siewert, R. A. Sobash, P. T. Marsh, A. R. Dean, M. Xue, F. Kong, K. W. Thomas, Y. Wang, K. Brewster, J. Gao, X. Wang, J. Du, D. R. Novak, F. E. Barthold, M. J. Bodner, J. J. Levit, C. B. Entwistle, T. L. Jensen, J. C. Correia, 2012: An Overview of the 2010 Hazardous Weather Testbed Experimental Forecast Program Spring Experiment. Bulletin of the American Meteorological Society, 139, 55-74.

The NOAA Hazardous Weather Testbed (HWT) conducts annual spring forecasting experiments organized by the Storm Prediction Center and National Severe Storms Laboratory to test and evaluate emerging scientific concepts and technologies for improved analysis and prediction of hazardous mesoscale weather. A primary goal is to accelerate the transfer of promising new scientific concepts and tools from research to operations through the use of intensive real-time experimental forecasting and evaluation activities conducted during the spring and early summer convective storm period. The 2010 NOAA/HWT Spring Forecasting Experiment (SE2010), conducted 17 May through 18 June, had a broad focus, with emphases on heavy rainfall and aviation weather, through collaboration with the Hydrometeorological Prediction Center (HPC) and the Aviation Weather Center (AWC), respectively. In addition, using the computing resources of the National Institute for Computational Sciences at the University of Tennessee, the Center for Analysis and Prediction of Storms at the University of Oklahoma provided unprecedented real-time conterminous United States (CONUS) forecasts from a multimodel Storm-Scale Ensemble Forecast (SSEF) system with 4-km grid spacing and 26 members and from a 1-km grid spacing configuration of the Weather Research and Forecasting model. Several other organizations provided additional experimental high-resolution model output. This article summarizes the activities, insights, and preliminary findings from SE2010, emphasizing the use of the SSEF system and the successful collaboration with the HPC and AWC.

Cocks, S. B., D. S. Berkowitz, R. Murnan, J. A. Schultz, S. Castleberry, K. Howard, K. Elmore, S. Vasiloff, 2012: Initial assessment of the dual-polarization quantitative precipitation estimate algorithm's performance for two dual-polarization WSR-88Ds.. Proc. 28th Conference on Interactive Information Processing Systems (IIPS), New Orleans, LA, USA, American Mteorological Society, CD-ROM, 7.B2.

By the end of July 2011, seven Weather Surveillance Radar 1988, Doppler (WSR-88D), radars were upgraded to Dual Polarization (DP) capabilities. As part of this effort, the Radar Operation Center's Applications Branch and the National Severe Storms Laboratory's (NSSL) Storm-Scale Hydrometeorology group are working together to evaluate the performance of the new DP Quantitative Precipitation Estimate (QPE) algorithm. An initial assessment was recently completed for two of the new DP radars: the KOUN DP prototype located in Norman, OK and KVNX located at Vance AFB, OK.
For KOUN, six warm season rain events were analyzed. DP QPE and the legacy Precipitation Processing System (PPS) estimates were compared with Oklahoma Climate Survey (OCS) rain gauges. Bias Error, defined as the radar rain estimate minus the gauge amount, and the Root Mean Square Error (RMSE) were calculated for each radar estimate paired to a co-located OCS rain gauge, henceforth called radar/gauge (R/G) pairs. Non-parametric statistical methods were used to calculate if the differences between DP QPE and PPS statistics were significant. Over 500 R/G pairs were examined. The results indicated DP QPE and PPS Bias errors were not significantly different. However, the RMSE was significantly lower for the DP QPE estimates when compared to the PPS estimates.

Similarly, ten warm season rain events and over 400 R/G pairs were examined using KVNX radar data. As with KOUN, the KVNX results were similar with RMSE values lower for DP QPE. For both KOUN and KVNX, the degree of improvement of the DP QPE RMSE over the PPS increased with heavier rain events/more convectively active weather. This result was expected as the DP QPE was expected to out-perform the legacy PPS system when hail contamination is present.

Available online at http://ams.confex.com/ams/92Annual/webprogram/Paper203568.html.

Cohn, S. J., J. Hallett, J. M. Lewis, 2006: Teaching graduate atmospheric measurement. Bulletin of the American Meteorological Society, 87, 1673-1678.

Coniglio, M. C., J. S. Kain, S. J. Weiss, D. R. Bright, J. J. Levit, M. Xue, M. L. Weisman, Z. I. Janjic, M. Pyle, J. Du, D. J. Stensrud, 2007: Evaluating WRF model output for severe-weather forecasting: The 2007 NOAA HWT Spring Experiment.. Extended Abstracts, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, American Meteorological Society, CD-ROM, 11A.2.

Coniglio, M. C., J. S. Kain, S. J. Weiss, D. R. Bright, J. J. Levit, G. W. Carbin, K. W. Thomas, F. Kong, M. Xue, M. L. Weisman, M. E. Pyle, K. L. Elmore, 2008: Evaluation of WRF model output for severe-weather forecasting from the 2008 NOAA Hazardous Weather Testbed Spring Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 12.4. [Available from Michael C. Coniglio, NSSL, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142060.htm.

Conway, J. B., D. Nealson, J. J. Stagliano, A. V. Ryzhkov, D. S. Zrnic, 2005: A New C-band Polarimetric Radar with Simultaneous Transmission for Hydrometeor Classification and Rainfall Measurements. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P12R.14.

Conway, J. B., A. Ryzhkov, D. Mitchell, P. Zhang, L. Venkatramani, J. L. Alford, D. Nelson, 2007: Examination of tornadic signatures observed at very close range using simultaneous dual-polarization radar at C band. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P10.2.

Corfidi, S. F., S. J. Weiss, J. S. Kain, S. J. Corfidi, R. M. Rabin, J. L. Levit, 2010: Revisiting the 3-4 April 1974 super outbreak of tornadoes. Weather and Forecasting, 25, .

The Super Outbreak of tornadoes over the central and eastern United States on 3–4 April 1974 remains the most outstanding severe convective weather episode on record in the continental United States. The outbreak far surpassed previous and succeeding events in severity, longevity, and extent. In this paper, surface, upper-air, radar, and satellite data are used to provide an updated synoptic and subsynoptic overview of the event. Emphasis is placed on identifying the major factors that contributed to the development of the three main convective bands associated with the outbreak, and on identifying the conditions that may have contributed to the outstanding number of intense and long-lasting tornadoes. Selected output from a 29-km, 50-layer version of the Eta forecast model, a version similar to that available operationally in the mid-1990s, also is presented to help depict the evolution of thermodynamic stability during the event.

Curtis, C. D., T. Y. Yu, 2007: Beam multiplexing on the NWRT: looking ahead. Preprints, 23rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, AMS, CD-ROM, 7.9.

Beam multiplexing is a weather radar scanning strategy that utilizes the electronic beam steering capability of a phased array antenna. When scanning with a parabolic dish antenna, contiguous samples are collected and processed. With beam multiplexing, the time between transmitted pulses or groups of pulses at a particular beam location is increased which reduces the correlation between samples. Because the samples are less correlated, fewer pulses are transmitted to achieve the same level of errors. The dead time between collections at a given beam location can be used to acquire data at other beam locations so that the radar is in constant use. Decreasing VCP update times is the primary advantage compared to transmitting contiguous pulses, but beam multiplexing also introduces new challenges that need to be considered.

A simple beam multiplexing strategy has been implemented on the National Weather Radar Testbed (NWRT). Weather radar time-series data were collected and analyzed using the phased array radar (PAR) which confirmed earlier theoretical predictions about reductions in VCP times. Because of limitations in the currently implemented approach, we are looking ahead to new approaches that fully realize the potential of beam multiplexing. This paper will introduce the fundamental concepts of beam multiplexing, discuss the advantages and drawbacks, and describe a new approach that addresses some of the limitations of the current strategy.

Available online at http://ams.confex.com/ams/pdfpapers/117073.pdf.

Curtis, C. D., S. M. Torres, 2011: Efficient range oversampling processing on the National Weather Radar Testbed. Extended Abstracts, 27th Conference on Interactive Information and Processing Systems (IIPS), Seatlle, WA, USA, Amer. Meteor. Soc., 13B.6.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Manuscript/Paper184552/Range%20Oversampling%20-%20AMS2011.pdf.

Curtis, C. D., S. M. Torres, 2010: Range oversampling techniques on the National Weather Radar Testbed. Extended Abstracts, 26th Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., 15B.3.

Available online at http://ams.confex.com/ams/pdfpapers/164389.pdf.

Curtis, C. D., D. S. Zrnic, T. Y. Yu, 2009: Spectral characterization of ground clutter using the NWRT. Extended Abstracts, 34th Conference on Radar Meteorology, Wiiliamsburg, VA, USA, Amer. Meteor. Soc., P10.15.

Available online at http://ams.confex.com/ams/pdfpapers/155724.pdf.

Curtis, C. D., D. S. Zrnic, T. Y. Yu, 2009: Staggered PRT beam multiplexing on the NWRT: Comparisons to existing scanning strategies. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P10.16.

Available online at http://ams.confex.com/ams/pdfpapers/155713.pdf.

Curtis, C. D., S. M. Torres, 2011: Adaptive Range Oversampling to Achieve Faster Scanning on the National Weather Radar Testbed Phased-Array Radar. Journal of Atmospheric and Oceanic Technology, 28, 1581-1597.

This paper describes a real-time implementation of adaptive range oversampling processing on the National Weather Radar Testbed phased-array radar. It is demonstrated that, compared to conventional matched-filter processing, range oversampling can be used to reduce scan update times by a factor of 2 while producing meteorological data with similar quality. Adaptive range oversampling uses moment-specific transformations to minimize the variance of meteorological variable estimates. An efficient algorithm is introduced that allows for seamless integration with other signal processing functions and reduces the computational burden. Through signal processing, a new dimension is added to the traditional trade-off triangle that includes the variance of estimates, spatial coverage, and update time. That is, by trading an increase in computational complexity, data with higher temporal resolution can be collected and the variance of estimates can be improved without affecting the spatial coverage.

Curtis, C. D., M. Yeary, 2011: Mitigating ground clutter using the multi-channel receiver on the National Weather Radar Testbed. Extended Abstracts, 35th Conference on Radar Meteorology, Pittsburgh, PA, USA, American Meteorological Society, 16B.3B.

The National Weather Radar Testbed (NWRT) provides a unique opportunity to test the effectiveness of using sidelobe cancelling channels to mitigate ground clutter. Sidelobe cancelling channels are receive-only auxiliary channels that are separate from the main array. These types of channels have already been used on wind profiling radars to mitigate ground clutter, and some of the same techniques can be applied to weather surveillance radars. With the recent deployment of an eight-channel multi-channel receiver on the NWRT, the sum channel and sidelobe channel data can be recorded and processed to research different techniques for addressing ground clutter contamination. This paper will examine some of the existing algorithms for employing sidelobe cancellers especially in the context of weather surveillance radars and the NWRT in particular. The multi-channel receiver project is a collaboration between the OU Atmospheric Radar Research Center and the National Severe Storms Laboratory.

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper191208.html.

Curtis, C. D., M. Yeary, R. D. Palmer, 2012: Using the Multi-Channel Receiver to Study Sidelobe Cancellation on the National Weather Radar Testbed. Extended Abstracts, 28th Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, Amer. Meteor. Soc., 6B.5.

The National Weather Radar Testbed (NWRT) provides a unique opportunity to study the effectiveness of sidelobe cancellation for mitigating ground clutter. The testbed is made up of a phased array antenna that has several receive-only auxiliary apertures that are separate from the main array and an eight-channel receiver for archiving multiple channels of time series data. This multi-channel receiver is a collaborative project between the OU Atmospheric Radar Research Center and the National Severe Storms Laboratory. Sidelobe channels have previously been utilized on wind profiling radars to mitigate ground clutter, and some of the same techniques should also be applicable to weather surveillance radars. The sum and sidelobe channel data can be recorded and processed to explore different approaches for addressing ground clutter contamination. This paper will examine some of the existing algorithms for employing sidelobe cancellers and apply these algorithms to collected time series data. This could lead to new ways to mitigate ground clutter on weather surveillance radars in the future.

Available online at http://ams.confex.com/ams/92Annual/webprogram/Paper197714.html.

Dodson, A., S. Van Cooten, K. Howard, J. Zhang, X. Xu, 2008: Assessing Vertical Profiles of Reflectivity (VPR's) To Detect Extreme Rainfall: Implications for Flash Flood Monitoring and Prediction. Preprints, 22nd Conference on Hydrology- Session 1, Weather To Climate Scale Hydrological Forecasting, New Orleans, LA, USA, AMS, CD-ROM, 1.5.

Tropical Storm Barry moved across the state of Florida from Tampa to Jacksonville on June 2 and then became extratropical as it moved northeast along the coastlines of Georgia, South Carolina and North Carolina from June 3 to June 4, 2007. Rainfall reports from gauges located within the surveillance areas of the Wakefield, Virginia (AKQ), Raleigh-Durham, North Carolina (RDU), and Morehead City, North Carolina (MHX), NEXRAD sites were collected and processed to document hourly rainfall rates associated with the system. In addition to the gauge data, atmospheric soundings from six area upper air observing sites were archived and analyzed to determine the response of atmospheric conditions, specifically freezing level, precipitable water, and atmospheric instability, as the system affected the region.

NOAA's National Severe Storms Laboratory (NSSL) Q2 System (www. nmq.nssl.noaa.gov) produces Vertical Profiles of Reflectivity (VPR) every five minutes for each continental United States (CONUS) NEXRAD site. These VPRs are used in the production of five-minute multi-sensor Quantitative Precipitation Estimates (QPE) to provide constantly updated relationships between radar reflectivity factor, Z, and rain rate, R (Z-R). VPRs were archived for June 3 and 4 for AKQ, RDU, and MHX. The VPRs were analyzed to quantify radar reflectivity trends over the course of the storm event. These trends were then correlated with rainfall rates, atmospheric sounding data, and surface observations, to investigate the characteristics of the VPRs associated with the highest rainfall rates. Results of this analysis indicate VPRs associated with the highest hourly rainfall rates observed with the storm system occurred as VPRs lost a concentrated area of high reflectivities around the atmospheric freezing level. Additionally, the gradient of radar reflectivities above and below this dissipating high reflectivity area diminished. Atmospheric soundings and surface map analysis indicated the air mass characteristics were acquiring tropical characteristics as surface dew points and atmospheric water content were increasing, wind directions transitioned from westerly to an easterly fetch off the Atlantic Ocean, and the atmospheric freezing level was rising. As the storm system moved away from the Carolinas, VPRs began to regain a concentrated area of high reflectivities around the atmospheric freezing level and the gradient of radar reflectivities began to increase once again above and below the area of higher reflectivities.

To quantify the implications of these VPR characteristics on the accuracy of the Q2 system's five-minute multi-sensor Quantitative Precipitation Estimates (QPE), the Q2 statistical verification tools were used to evaluate the performance of the system during the periods of the most intense rainfall. The Q2 system has recently implemented a tropical rain Z-R when VPRs and atmospheric sounding data meet criteria which have been identified by NSSL scientists as common factors in intense rainfall events. The VPRs observed through this June, 2007 storm event, were consistent with their findings. Results of this assessment show the Q2 tropical Z-R relationship produced highly accurate precipitation estimates which are available at a 1 km grid mesh resolution every five minutes. Additionally, the dynamic VPR system captured the air mass changes which occurred during the event. This feature provides improved information on a storm's environment to determine appropriate radar Z-R adjustments. This case demonstrates the ability to increase the accuracy of precipitation estimates especially in ungauged locations which can improve NOAA and our nation's flash flood monitoring and prediction programs.

Available online at http://ams.confex.com/ams/88Annual/techprogram/paper_135143.htm.

Dotzek, N., R. M. Rabin, L. D. Carey, D. R. MacGorman, T. L. McCormick, N. W. Demetriades, M. J. Murphy, R. L. Holle, 2005: Lightning activity related to satellite and radar observations of a mesoscale convective system over Texas on 7-8 April 2002. Atmospheric Research, 76(1-4), 127-166.

A multi-sensor study of the leading-line, trailing-stratiform (LLTS) mesoscale convective system (MCS) that developed over Texas in the afternoon of 7 April 2002 is presented. The analysis relies mainly on operationally available data sources such as GOES East satellite imagery, WSR-88D radar data and NLDN cloud-to-ground flash data. In addition, total lightning information in three dimensions from the LDAR II network in the Dallas-Ft. Worth region is used. GOES East satellite imagery revealed several ring-like cloud top structures with a diameter of about 100 km during MCS formation. The Throckmorton tornadic supercell, which had formed just ahead of the developing linear MCS, was characterized by a high CG+ percentage below a V-shaped cloud top overshoot north of the tornado swath. There were indications of the presence of a tilted electrical dipole in this storm. Also this supercell had low average CG-first stroke currents and flash multiplicities. Interestingly, especially the average CG+ flash multiplicity in the Throckmorton storm showed oscillations with an estimated period of about 15 min. Later on, in the mature LLTS MCS, the radar versus lightning activity comparison revealed two dominant discharge regions at the back of the convective leading edge and a gentle descent of the upper intracloud lightning region into the trailing stratiform region, apparently coupled to hydrometeor sedimentation. There was evidence for an inverted dipole in the stratiform region of the LLTS MCS, and CG+ flashes from the stratiform region had high first return stroke peak currents.

Douglas, M. W., T. Killeen, J. F. Mejia, 2006: Use of MODIS and GOES imagery to help delineate the distribution of cloud forests along the eastern Andean slopes.. Preprints, (14th Conference on Satellite Meteorology and Oceanography), Atlanta, GA, USA, American Meteorological Society, P3.18. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

The environment with the greatest biodiversity from a global standpoint is that known as the tropical Andes “hotspot”, which is a broad region along the eastern slopes of the Andes in South America. One of the subregions with the highest diversity within this region is the cloud forest, a region of very high cloudiness and high annual precipitation. Mapping the cloud forest and surrounding environments has been of high priority because resources for conservation are limited and conservation organizations and governmental agencies need to know what areas should receive highest priority for protection efforts.

Work associated with the South American Low-level Jet Experiment (SALLJEX) carried out in 2002-3 led to the use of GOES imagery to develop composites of visible and IR imagery for describing the mean cloudiness along the eastern slopes of the Andes. More recently MODIS imagery has been used to describe cloudiness at even higher resolution. Together, these imagery sources provide clues as to the distribution of cloudiness that can be related to cloud forest environment. In addition, dry canyon environments, the locus of many geographically-restricted species, can likewise be readily described from the cloudiness composites.

The GOES and MODIS cloudiness composites will be shown, and some limitations of inferring cloud forest locations and dry canyon habitat from the imagery will be discussed. The potential for this technique to be applied to other areas will be mentioned.

Doviak, R. J., 2005: A phased-array radar for weather research and education. Proc. XXVIIIth General Assembly of International Union Radio Science (URSI), New Delhi, India, URSI, CD-ROM, FP.8. [Available from Dick Doviak, NSSL, 120 David Boren Blvd, Norman, OK, USA, 73072-7327.]

The National Severe Storms Laboratory has assembled the first agile-beam phased-array Doppler radar for weather research and education. This National Weather Radar Testbed (NWRT) will support testing of ideas to observe weather, and other objects. Mechanically steered beams inefficiently use radar resources, and are limited in providing timely and added information on weather (e.g., the NWRT could directly measure crossbeam wind). Because the NWRT’s beam can be electronically steered to observe only weather of interest, rapid observations can be made, and/or the radar could serve other purposes (e.g., tracking aircraft, etc.), while conserving spectral space.

Doviak, R. J., G. Zhang, 2006: Crossbeam Wind Measurements with Phased_Array Doppler Weather Radar. Extended Abstracts, Fourth European Conference on Radar in Meteorlogy and Hydrology, Barcelona, Spain, Many, 1-4. [Available from Dick Doviak, NSSL, 120 David Boren Blvd, Norman, OK, USA, 73072-7327.]

Doviak, R. J., M. Fang, V. Melnikov, G. Zhang, 2008: Theoretical and practical considerations in using spectrum width data. Extended Abstracts, European Conference on Radar Meteorology - 2008, Helsinki, Finland, Vaisala, CD-ROM, 2.4.

Doviak, R. J., L. Lei, G. Zhang, J. Meier, C. Curtis, 2011: Comparing Theory and Measurements of Cross-Polar Fields of a Phased Array Weather Radar. IEEE Geoscience and Remote Sensing Letters, 8, 1002-1006.

Cross-polar measurements made with an agile-beam phased-array weather radar are compared with theory. The intensity of cross-polar fields places conditions on the accuracy of meteorological measurements. Results reported herein support the hypothesis that polarimetric phased-array radar for weather observations can be designed to allow use of the polarimetric data acquisition mode being implemented by the National Weather Service on upgraded WSR-88Ds which use parabolic reflector antennas.

Dowell, D. C., C. R. Alexander, J. M. Wurman, L. J. Wicker, 2005: Centrifuging of hydrometeors and debris in tornadoes: Radar-reflectivity patterns and wind-measurement errors. Monthly Weather Review, 133, 1501-1524.

High-resolution Doppler radar observations of tornadoes reveal a distinctive tornado-scale signature with the following properties: a reflectivity minimum aloft inside the tornado core (described previously as an "eye"), a high-reflectivity tube aloft that is slightly wider than the tornado core, and a tapering of this high-reflectivity tube near the ground. The results of simple one-dimensional and two-dimensional models demonstrate how these characteristics develop. Important processes in the models include centrifugal ejection of hydrometeors and/or debris by the rotating flow and recycling of some objects by the near-surface inflow and updraft.

Doppler radars sample the motion of objects within the tornado rather than the actual airflow. Since objects move at different speeds and along different trajectories than the air, error is introduced into kinematic analyses of tornadoes based on radar observations. In a steady, axisymmetric tornado, objects move outward relative to the air and move more slowly than the air in the tangential direction; in addition, the vertical air-relative speed of an object is less than it is in still air. The differences between air motion and object motion are greater for objects with greater characteristic fall speeds (i.e., larger, denser objects) and can have magnitudes of tens of meters per second. Estimates of these differences for specified object and tornado characteristics can be obtained from an approximation of the one-dimensional model.

Doppler On Wheels observations of the 30 May 1998 Spencer, South Dakota, tornado demonstrate how the apparent tornado structure can change when the radar-scatterer type changes. When the Spencer tornado entered the town and started lofting debris, changes occurred in the Doppler velocity and reflectivity fields that are consistent with an increase in mean scatterer size.

Du Chatelet, J. P., M. Tahanout, C. Curtis, 2010: Experimental validation of a multiple PRT weather radar transmitting scheme optimized to mitigate wind speed ambiguities and to filter-out ground clutter. Proc. 6th European Conf. on Radar in Meteorology and Hydrology: Adv. in Radar Technology (ERAD), Sibiu, Romania, National Meteorological Administration, Romania, Session 13.

Available online at http://www.erad2010.org/pdf/oral/wednesday/advances2/2_ERAD2010_218.pdf.

Ellis, S. M., M. Dixon, G. Meymaris, S. Torres, J. Hubbert, 2005: Radar range and velocity ambiguity mitigation: Censoring methods for the SZ-1 and SZ-2 phase coding algorithms. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, 19.3.

Elmore, K. L., K. A. Scharfenberg, C. Legett, 2007: The NSSL winter hydrometeor classification ground truth program: Public involvement in science. Preprints, 31st Intl. Conf. on Radar Meteor., Cairns, Australia, Amer. Meteor. Soc., CD-ROM, P10.9.

During the winter of 2006-2007, a concerted effort was made by the National Severe Storms Laboratory to collect polarimetric radar data using the KOUN radar during winter precipitation events. Simultaneously, observations of precipitation type within a radius of 150 km of KOUN were solicited from the public. Public response has resulted in about 2500 individual observations of winter precipitation type over the course of three major events. These data are intended to be used to both verify the current hydrometeor classification algorithm performance in winter weather events, and to enhance the algorithm's performance. This paper discusses the nature of the ground truth data collected, its overall utility, the nature and scope of quality assurance checking, how event timing affects observation availability, how best to solicit and encourage public participation, and examples of how the data are being used.

Emersic, C., D. MacGorman, T. Schuur, N. Lund, C. Payne, E. Bruning, 2007: Lightning activity relative to the microphysical and kinematic structure of storms during a thunder-snow episode on 29-30 November 2006. Preprints, 2007 Fall Meeting, San Francisco, CA, USA, American Geophysical Union, AE43A-01.

We have examined lightning activity relative to the microphysical and kinematic structure of a winter thunderstorm complex (a thunder-snow episode) observed east of Norman, Oklahoma during the evening of 29-30 November 2006. Polarimetric radar provided information about the type of particles present in various regions of the storms. The Lightning Mapping Array (LMA) recorded VHF signals produced by developing lightning channels. The times of arrival of these lightning signals across the array were then used to reconstruct the location and structure of lightning, and these reconstructions were overlaid with radar data to examine the relationship between lightning properties and storm particle types.

Four storms in this winter complex have been examined. It was inferred from lightning structure that, in their mature stage, all cells we examined had a positive tripole electrical structure (an upper positive charge center, a midlevel negative charge center, and a lower positive charge center). The storms began with lightning activity in the lower dipole (lower positive and midlevel negative regions), but this evolved into lightning activity throughout the tripole structure within approximately 15-20 minutes. In the longer lived storms, the mature stage lasted for approximately 1.5-2 hours. During this stage, the lower positive charge region was situated less than 5 km above ground, the midlevel negative charge region was typically above 5 km, and the upper positive charge region was located at an altitude of less than 10 km in all the storm cells analyzed. The charge regions descended over approximately the last 30 minutes of lightning activity, the lower charge regions eventually reaching ground. This resulted in the loss of the lower positive charge center and the subsequent diminishment of the lower negative charge center.

Emersic, C., P. L. Heinselman, D. R. MacGorman, E. Bruning, 2011: Lightning activity in a hail-producing storm observed with phased-array radar. Monthly Weather Review, 139, 1809-1825.

This study examined lightning activity relative to the rapidly evolving kinematics of a hail-producing storm on 15 August 2006. Data were provided by the National Weather Radar Testbed Phased-Array Radar, the Oklahoma Lightning Mapping Array, and the National Lightning Detection Network.

This analysis is the first to compare the electrical characteristics of a hail-producing storm with reflectivity and radial velocity structure at temporal resolutions of <1 min. Total flash rates increased to ~220 / min as the storm’s updraft first intensified, leveled off during its first mature stage, and then decreased for 2–3 min despite the simultaneous development of another updraft surge. This reduction in flash rate occurred as wet hail formed in the new updraft and was likely related to the wet growth; wet growth is not conducive to hydrometeor charging and probably contributed to the formation of a “lightning hole” without a mesocyclone. Total flash rates subsequently increased to ~450 / min as storm volume and inferred graupel volume increased, and then decreased as the storm dissipated. Vertical charge structure in the storm initially formed a positive tripole (midlevel negative charge between upper and lower positive charges). Charge structure in the second updraft surge consisted of negative charge above deep midlevel positive charge, a reversal consistent with the effect of large liquid water contents on hydrometeor charge polarity in laboratory experiments. Prior to the second updraft surge, the storm produced two cloud-to-ground flashes, both lowering the usual negative charge to ground. Shortly before hail likely reached ground, the storm produced four cloud-to-ground flashes, all lowering positive charge. Episodes of high singlet VHF sources were observed at ~13–15 km during the initial formation and later intensification of the storm’s updraft.

Erlingis, J. M., J. J. Gourley, T. Smith, K. L. Ortega, 2009: Development of a detailed database of flash flood observations. Extended Abstracts, 23rd Conf. on Hydrology, Phoenix, AZ, USA, AMS, JP2.8.

The primary tool used in the National Weather Service to provide guidance toward the likelihood of imminent flash flooding is the Flash Flood Monitoring and Prediction system (FFMP). FFMP “triggers” when rainfall amounts exceed a 1-, 3-, or 6-hour accumulation threshold, or flash flood guidance (FFG), over basins less than 260 km2. It has been noted that legacy or county-wide FFG values are derived from soil states produced by the Sacramento model which operates on basins up to 4000 km2 at a 6-hourly time step. New, gridded approaches toward deriving FFG (GFFG) have emerged in order to address this scale mismatch. A high-resolution, accurate flash flood observation database was needed in order to evaluate the new GFFG methods relative to the legacy FFG approach.

The Severe Hazards Analysis and Verification Experiment (SHAVE) has been in operation at the National Severe Storms Laboratory since 2006. Undergraduate students use radar-based products and digital telephone databases, all accessible within Google Earth, in order to call and poll the public about the occurrence and severity of hail, wind, and now flash floods. This paper discusses the criteria used to prompt phone calls and the information requested from the public. We show statistics and make some initial inferences based on the flood calls that were made during the summer of 2008. It is envisioned that this database combined with streamflow observations and Storm Data reports will lead to better tools to predict the likelihood of flash floods.

Available online at http://ams.confex.com/ams/89annual/techprogram/paper_148661.htm.

Fang, M., R. J. Doviak, 2005: Corrections to and considerations of the spectrum width equation. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P4R.2.

Fang, M., J. Zhang, J. K. Williams, J. A. Craig, 2008: Three-Dimensional Mosaic of the Eddy Dissipation Rate Fields from WSR-88Ds. Extended Abstracts, The 88th AMS annual conference, New Orleans, LA, USA, AMS, P4.5. [Available from Ming Fang, 408C, Wadsack Dr., Norman, OK, USA, 73072.]

A national 3-D mosaic of Eddy Dissipation Rate (EDR) is being developed, prototyped, and evaluated through collaboration between the National Center for Atmospheric Research (NCAR) and NOAA’s National Severe Storms Lab (NSSL) under the auspices of the FAA Aviation Weather Research Program’s Turbulence and Advanced Weather Radar Techniques (AWRT) Research Teams. The EDR field is an indicator of in-cloud turbulence intensity derived from individual WSR-88Ds’ spectrum width data by the NEXRAD Turbulence Detection Algorithm (NTDA), which was developed at NCAR by the Turbulence Research Team. The NTDA software has been delivered to the National Weather Service and will be implemented operationally on all WSR-88Ds beginning in the spring of 2008, providing EDR and associated confidence data as a polar-grid Level III field. A national 3-D mosaic of the EDR field will provide a high-resolution, rapid update, in-cloud turbulence product for use in aviation safety decision support products. In particular, the Turbulence Research Team plans to incorporate it into a new rapid-update version of the Graphical Turbulence Guidance product, which will directly address convective turbulence for the first time.

The EDR mosaic has been developed using NTDA data from 20 radars covering the Chicago to Washington DC region that are being generated at NCAR and transferred to NSSL in real-time. A mosaic scheme previously developed by the AWRT Research Team for creating 3-D reflectivity mosaics was used as a starting point, but differences between EDR and reflectivity has required a number of adjustments; in addition, the 3-D mosaic scheme was modified to utilize the confidence values produced by the NTDA. The prototype regional 3-D in-cloud turbulence mosaic was evaluated based on comparisons with EDR values obtained from an automated measurement and reporting system on United Airlines aircraft. Continuing evaluation and tuning efforts are expected to lead to enhancements in the current mosaic scheme and establishment of a methodology that will eventually be used in the operational national 3-D in-cloud turbulence mosaic.

Fang, M., R. J. Doviak, P. Zhang, 2008: An Analytical Expression For Doppler Spectra Related to TerminalVelocity With Non-uniform Drop Size Distribution. Extended Abstracts, The 88th AMS annual meeting, New Orleans, LA, USA, AMS, P2.27. [Available from Ming Fang, 408C, Wadsack Dr., Norman, OK, USA, 73072.]

Starting from the correlation function and neglecting other spectrum broadening mechanisms, an analytical expression for the Doppler spectrum is related to the drop’s terminal velocity and size distribution if there is a unique relationship between drop’s diameter and its terminal velocity. The derivation does not require drop size distribution to be homogeneous. This generalized expression reduces to previously derived expression if drop size distribution is uniform.

Fang, M., R. J. Doviak, 2008: WSR-88D Observed Spatial Spectra of Turbulence in Precipitation. Extended Abstracts, The 88th AMS annual meeting, New Orleans, LA, USA, AMS, 12.6. [Available from Ming Fang, 408C, Wadsack Dr., Norman, OK, USA, 73072.]

Different algorithms are designed to isolate the turbulent component from radar measured Doppler velocity. Spatial spectra along the quasi-horizontal direction are then obtained in stratiform rain, storms and squall lines. The slope of horizontal spectra in stratiform rain and storms is close to -5/3 on a log-log graph up to at least scales of 10 km and 7 km respectively. The spectrum in a squall line has a steeper slope than -5/3 up to scales at least 17 km. The scales at low wave number end on the spectra are so large that the spectra could not be due to three-dimensional isotropic turbulence but to two-dimensional turbulence.

Fang, M., . Doviak, 2008: Coupled Contributions in the Doppler Radar Spectrum Width Equation. Journal of Atmospheric and Oceanic Technology, 25, .

Fang, M., R. J. Doviak, 2008: Coupled Contributions in the Doppler Radar Spectrum Width Equation. Journal of Atmospheric and Oceanic Technology, 25, 2245-2258.

Contrary to accepted usage, the second central moment of the Doppler spectrum is not the sum of the second central moments of individual spectral broadening mechanisms. A rigorous theoretical derivation of the spectrum width observed with short dwell-times reveals that the sum cannot be strictly taken for the variances associated with various spectral broadening mechanisms, and that an added term coupling shear with turbulence is needed. Furthermore, shear and antenna rotation are coupled. The theoretical expressions derived herein apply to radars with fixed or scanning beams.

Fang, M., R. J. Doviak, 2011: Significance of the Coupled Term in the Doppler Weather Radar Spectrum Width Equation.. Journal of Atmospheric and Oceanic Technology, 28, 539-547.

There is an additional zero mean random variable term that couples mean wind shear and turbulence in the Doppler radar spectrum width equation. This random variable, labeled the “coupled term”, has been neglected heretofore in the literature. Herein the variance of the squared spectrum width ascribed to this coupled term is determined from data collected with a WSR-88D in two snow storms; it can exceed 1 m^4 s^-4. Thus this coupled term can be a significant contributor to the variance of the spectrum width and must be considered when using spectrum width to deduce turbulence.

Fast, J. D., R. K. Newsom, K. J. Allwine, Q. Xu, P. Zhang, J. H. Copeland, J. Sun, 2007: Using NEXRAD wind retrievals as input to atmospheric dispersion models. Extended Abstracts, Seventh Symposium on the Urban Environment, San Diego, CA, USA, Amer. Meteor. Soc., 8.2.

Available online at http://ams.confex.com/ams/7Coastal7Urban/techprogram/paper_127244.htm.

Fast, J. D., R. K. Newsom, K. J. Allwine, Q. Xu, P. Zhang, J. Copeland, J. Sun, 2008: An evaluation of two NEXRAD wind retrieval methedologies and their use in atmospheric dispersion models. Journal of Applied Meteorology and Climatology, 47, 2351-2371.

Feltz, W. F., K. Bah, K. Bedka, J. Gerth, J. S. Kain, S. Lindstrom, J. Otkin, T. Schmidt, J. Sieglaff, C. Siewert, R. Rabin, 2010: UW-CIMSS GOES-R Proving Ground Participation in Storm Prediction Center Hazardous Weather Testbed. Preprints, 17th Conference on Satellite Meteorology and Oceanography, Annapolis, MD, USA, Amer. Meteor. Soc.,, P9.9.

Fierro, A. O., L. Leslie, E. R. Mansell, G. J. Holland, J. M. Straka, 2006: Numerical simulations of the evolution of tropical cyclone electrification, lightning, microphysics, and dynamics at landfall: preliminary results. Preprints, Second Conference on Meteorological Applications of Lightning Data, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P1.12.

Providing accurate and timely forecasts of the intensity and location of landfalling tropical cyclones (TCs) is a major meteorological challenge, and is increasingly important as coastal regions affected become more populated. A major unsolved problem is why TCs vary so much in their electrical activity. Some storms have little lightning activity, while others are extremely active, especially in their spiral cloud bands or within their eyewall as they intensify or weaken. At present, little is known about the evolution of charge and subsequent electrification in hurricanes, so our early results are a guideline for future studies. The findings are expected to have major implications for TC predictions and lightning observation strategies at landfall. We suggest that they may also lead to improved understanding of TC structure in general.

Toward this goal, a sophisticated cloud model featuring a 10-ICE microphysics scheme and a 3D branched lightning module explores the utility of a systematic monitoring of lightning activity such as flash rate, cloud to ground polarity and stroke multiplicity within TCs, as they strengthen or weaken over the ocean, especially when they make landfall. Of interest is how the microphysical and subsequent charge structure differs from, or resembles, that of electrically active continental convective systems such as supercells or mesoscale convective systems. A preliminary set of high-resolution numerical simulations were performed on a fine grid having a horizontal grid spacing of 3km and a vertical mean spacing of 600 m (45 height levels). The environmental initial conditions were from a composite sounding from TC Charley (2004), which showed a clear increase in lightning activity before intensifying from a borderline Category 3 to a high-end Category 4 storm on the Saffir-Simpson scale 8 hours before landfall on the west Florida coast. A meridionally orientated horizontal slab moving towards the TC at a fixed constant speed (of 8 m/s) was used as an initial simulation of landfall. More sophisticated landfall representations are being developed.

Preliminary results show that the highest total lightning flash rate are found within the stronger cells forming the outer rainbands and within the eyewall, where updraft speeds seldom exceed 15 m/s, consistent with observations. Significant charging capable to produce lightning flashes are collocated with regions having moderate graupel mixing ratio (> 0.5 g/kg) and moderate LWC (> 1 g/kg), namely within the eyewall and the strongest outer band cells. Using the Gardiner non-inductive scheme and weak inductive charging settings, the eyewall exhibits a normal tripole charge structure while a normal dipole is observed in the outer eyewall startiform region as induction responsible for the formation/enhancement of the lowest charge region becomes negligible there. The charges forming the dipole in the outer eyewall are generated within the eyewall via non-inductive collisional charging between graupel pellets and lighter ice crystals in the mixed-phase region at midlevels (~-15C isotherm level at 7km AGL) and are ejected radially outward by the centripetal force induced by the storm intense circulation at and near its center.

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_103235.htm.

Fierro, A. O., L. Leslie, E. Mansell, J. Straka, D. MacGorman, C. Ziegler, 2007: A High-resolution Simulation of Microphysics and Electrification in an Idealized Hurricane-like Vortex. Meteorology and Atmospheric Physics, 98, 13-33.

Cloud-to-ground (CG) lightning bursts in the eyewall of mature tropical cyclones (TCs) are believed to be good indicators of imminent intensification of these systems. While numerous well-documented observational cases exist in the literature, no modeling studies of the electrification processes within TCs have previously been conducted. At present, little is known about the evolution of charge regions and lightning activity in mature TCs. Towards this goal, a numerical cloud model featuring a 12-class bulk microphysics scheme with electrification and lightning processes is utilized to investigate the evolution of the microphysics fields and subsequent electrical activity in an idealized hurricane-like vortex.

Preliminary results show that the highest total lightning flash rates (CG plus intracloud) are primarily found within the eyewall where updraft speeds tend to be larger than elsewhere in the TC, though rarely exceeding 10 m s^-1. Smaller total flash rates are also found within the strongest cells forming the outer bands, where updraft speeds sometimes reach 15 m s^-1. As expected, these two regions of the storm are generally characterized by moderate total graupel mixing ratio (> 0.5 g kg^-1) and moderate cloud water content (> 0.2 g m^-3). When the model uses the Saunders and Peck non-inductive (NI) charging scheme and moderate inductive charging settings, the inner eyewall region exhibits a complex charge structure. However, the charge regions involved in lightning can be described as a normal tripole charge structure in the eyewall, while a normal dipole is observed in the outer eyewall stratiform region and in the strongest cells forming the outer rainbands. The charges forming the normal dipole in the outer eyewall are generated within the eyewall via NI charging in the mixed-phase region at mid-levels (near the -10 deg C isotherm) and later, are ejected radially outward by the storm’s intense circulation.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. J. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2005: The National Weather Radar Testbed (Phased-Array). Extended Abstracts, 32nd Confernce on Radar Meteorology, Alburqueue, NM, USA, American Meteorological Society, CD-ROM, 12R.3.

A new national asset for weather radar research is operational in Norman, Oklahoma. This project was developed as a result of a partnership between the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory, the United States Navy's Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma's Electrical and Computer Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration's Technical Center and Basic Commerce and Industries, Inc This project involved converting a Navy SPY-1 phased array antenna system into a weather research tool. The National Weather Radar Testbed (NWRT) provides the first phased array radar available on a full-time basis to the meteorological research community.
The NWRT became operational in September 2003, but initial problems delayed data collection until May 2004. In this paper, we will describe data quality improvements, recent upgrades, and future plans.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. J. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2006: Status report on the National Weather Radar Testbed (Phased-Array). Extended Abstracts, 22nd International Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, 11.1.

The National Weather Radar Testbed (NWRT) is operational in Norman, Oklahoma. This project was developed as a result of a partnership between the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory, the United States Navy's Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma's Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration's Technical Center and Basic Commerce and Industries, Inc Using a Navy SPY-1A phased array antenna system, the NWRT provides the first phased array radar available on a full-time basis to the meteorological research community.
The NWRT became operational in September 2003, and first data were collected in May 2004. Several data sets have been collected during the limited 2005 storm season. Current efforts are concentrated on improving the scanning speed through beam-multiplexing and preparing the system for remote operations. In this paper, we will describe the present status, research progress, and plans how to exploit the unique capabilities of electronic beam steering on the NWRT.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2005: Progress Report on the National Weather Radar Testbed (Phashed-Array).. Preprints, 21st International Conference on Interactive Information Processing Systems for Meteorology, Ocenography, and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 19.5.

A new national asset for weather radar research is operational in Norman, Oklahoma. This project was developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc This project involved converting a Navy SPY-1 phased array antenna system into a weather research tool. The National Weather Radar Testbed (NWRT) provides the first phased array radar available on a full-time basis to the meteorological research community.

The NWRT became operational in September 2003, but problems with the velocity channel delayed initial data collection until May 2004. Our initial efforts have been focused on ensuring that the data is of high quality. Qualitative comparisons with a WSR-88D (KTLX-Twin Lakes, OK) appear to be similar. In this paper, we will describe data quality improvements, recent upgrades, future plans and present some examples of the first tornadic data set obtained with this new national facility.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2007: Update on the National Weather Radar Testbed (Phased-Array). Preprints, The 23d Conference on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 7.4.

The National Weather Radar Testbed (NWRT) is now functioning as a research tool in Norman, Oklahoma. The NWRT was developed as a result of a partnership between the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory, the United States Navy's Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma's Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration's Technical Center and Basic Commerce and Industries, Inc.. Using a Navy SPY-1A phased array antenna system, the NWRT provides the first phased array radar available on a full-time basis to the meteorological research community and for testing of the concept of a multifunction phased array radar (MPAR) system.

Again, only a few data sets were collected during the 2006 storm season due to the limited amount of severe weather. Current efforts are concentrated on improving the scanning speed through beam-multiplexing and over-sampling. We have also implemented remote operations in preparation of our move to the National Weather Center. In this paper, we will describe the present status, research progress including eight second volume scans, and plans on making the NWRT a national resource.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, a. M. Shapiro, R. J. Vogt, W. Benner, 2007: Update on the National Weather Radar Testbed (Phased-Array). Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, American Meteorological Society, CD-ROM, 7.2.

The National Weather Radar Testbed (NWRT) is now functioning as a research tool in Norman, Oklahoma. The NWRT was developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc Using a Navy SPY-1A phased array antenna system, the NWRT provides the first phased array radar available on a full-time basis to the meteorological research community and for testing of the concept of a multi-mission phased array radar (MPAR) system.

Only a few data sets were collected during the 2006 storm season due to the limited amount of severe weather. Results from the 2007 storm season will be reported on along with planned system upgrades and a general overview of the research projects conducted in 2006 and 2007. We will also report on the progress of making the NWRT available as a national resource

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2008: Another Update on the National Weather Radar Testbed (Phased-Array). Extended Abstracts, The 24th Conference on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, American Meteorological Society, CD-ROM, 9A.1.

The National Weather Radar Testbed (NWRT) is now functioning as a research tool in Norman, Oklahoma. Developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the NWRT provides the first phased array radar available on a full-time basis to the meteorological research community and for testing of the concept of a multifunction phased array radar system.

The 2007 storm season provided an improved amount of severe weather for data collections supporting various research topics. In addition, the NWRT is being upgraded to support new research topics. The planning has just started for implementing a dual-polarized sub-array for testing the characteristics of a phased array dual polarized weather radar. The facility is now capable of supporting research projects from remote users. In this paper, we will describe the present status, future upgrades and research progress including results of high temporal volumetric scans of severe storms.

Forsyth, D., J. Kimpel, D. Zrnic, R. Ferek, J. Heimmer, T. McNellis, J. Crain, A. Shapiro, R. Vogt, W. Benner, 2008: The National Weather Radar Testbed (Phased-Array). Preprints, Fifth European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Finnish Meteorological Institute, 9.3.

The National Weather Radar Testbed (NWRT) is a phased array radar being used as a research tool in Norman, Oklahoma. Developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the NWRT provides the first phased array radar available on a full-time basis to the meteorological research community and for testing of the concept of a multifunction phased array radar system.

The 2007 storm season provided an improved amount of severe weather for data collections supporting various research topics. In addition, the NWRT is being upgraded to support new research topics. The planning has just started for implementing a dual-polarized sub-array for testing the characteristics of a phased array dual polarized weather radar. The facility is now capable of supporting research projects from remote users. In this paper, we will describe the present status, future upgrades and research progress including results of high temporal volumetric scans of severe storms.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2009: The National Weather Radar Testbed (Phased-Array) – A Progress Report. Extended Abstracts, 25th International Conference on Interactive Information and Processing Systems, Phoenix, AZ, USA, American Meteorological Soceity, 8B.2.

The National Weather Radar Testbed (NWRT) continued its role as a research tool in Norman, Oklahoma. Developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the NWRT provides the first phased array radar available on a full-time basis to the meteorological research community and for testing of the concept of a multifunction phased array radar system.

The 2008 storm season provided additional data on various severe weather events. In addition, the NWRT continued work on various upgrades to support new research topics. The planning continued for implementing a dual-polarized sub-array for testing the characteristics of a phased array dual polarized weather radar. In this paper, we will describe the present status, future upgrades and research progress including results of additional high temporal volumetric scans of severe storms.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2010: Progress Report on the National Weather Radar Testbed (Phased-Array). Extended Abstracts, 26th International Conference on Interactive Information And Processing Systems, Atlanta, GA, USA, American Meteorological Society, 14B.1.

Since 2003, the National Weather Radar Testbed (NWRT) has provided a testbed for evaluating phased array technology for use as part of a national network of surveillance radars. Developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the NWRT continues to test the concepts of a multi-function radar system and has become an educational component for the next generation of radar meteorologists and engineer.

With each passing storm season, we have continued to demonstrate the advantages of phased array radar. In this paper, we will describe the present status and future plans for the NWRT and provide examples of the latest results of our testing of the phased array technology.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. Ferek, J. F. Heimmer, T. J. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2009: Keynote Talk: What's new at the National Weather Radar Testbed (Phased-Array). Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, 8A.1.

For over six years, the National Weather Radar Testbed (NWRT) has continued its role as the multi-function phased array radar testbed in Norman, Oklahoma. Developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the NWRT continues to provide both meteorological and aircraft data for testing the concept of a multifunction phased array radar system. In addition, the NWRT has become an important component in the education of the forthcoming generation of radar meteorologists and engineers.

Each storm season has provided additional data on various severe weather events and an opportunity to demonstrate the advantages of using the phased array radar. We have added new features to the system each year and have continued our planning implementation of a dual-polarized sub-array for testing the characteristics of a phased array dual polarized weather radar. In this paper, we will describe the present status, future upgrades and research progress including results of additional high temporal volumetric scans of severe storms.

Forsyth, D. E., J. F. Kimpel, D. S. Zrnic, R. J. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, A. M. Shapiro, R. J. Vogt, W. Benner, 2011: What's new at the National Weather Radar Testbed (Phased-Array). Extended Abstracts, 27th International Conference on Interactive Information and Processing Systems, Seattle, WA, USA, American Meteorological Society, 12B.2.

A very different type of weather radar is being tested in Norman, Oklahoma at the National Severe Storms Laboratory. The technology being evaluated is a phased array antenna that provides electronic steering of the radar beam. As a result of the partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the National Weather Radar Testbed (NWRT) has been testing the concepts of a multi-function radar system since 2003.

The system continues to demonstrate the advantages of an agile beam weather and aircraft surveillance radar. In this paper, we will describe the present status and future plans for the NWRT and provide examples of the latest results of our testing of the phased array technology.

Forsyth, D. E., D. S. Zrnic, R. J. Ferek, J. F. Heimmer, T. McNellis, J. E. Crain, R. J. Vogt, W. Benner, 2011: Natioanl Weather Radar Testbed (Phased-Array): An outstanding platform for research and development.. Extended Abstracts, 35th Conference on Radar Meteorology, Pittsburg, PA, USA, American Meteorological Soceity, 14A.2.

The National Weather Radar Testbed (NWRT) has continued its research and development role as the multi-function phased array radar testbed in Norman, Oklahoma. Developed as a result of a partnership between the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, the United States Navy’s Office of Naval Research, Lockheed Martin Corporation, the University of Oklahoma’s Electrical and Computing Engineering Department and School of Meteorology, the Oklahoma State Regents for Higher Education, the Tri-Agencies' (Department of Commerce, Defense and Transportation) Radar Operations Center, the Federal Aviation Administration’s Technical Center and Basic Commerce and Industries, Inc, the NWRT continues to provide both meteorological and aircraft data for testing the concept of a multifunction phased array radar system. In addition, the NWRT has become a testbed for signal processing advancements and continues as an important component in the education of the forthcoming generation of radar meteorologists and engineers.

The testbed continues to provide important data on severe weather events and to demonstrate the advantages of using phased array technology. Participation by National Weather Service forecasters has expanded our knowledge concerning the benefits of fast scanning radars. New scanning strategies are being tested every year. In addition, our work on risk reduction continues on dual polarized phased array radars. In this paper, we will elaborate on our accomplishments and describe future work using the NWRT.

Fredrickson, S. E., P. L. Heinselman, D. Zaras, W. J. Gonzales-Espada, 2006: Relative Humidity: What do students know about it?. Preprints, 15th Educational Symposium, Atlanta, GA, USA, 86th AMS Annual Meeting, CD-ROM, 3.9. [Available from Sherman Fredrickson, National Severe Storms Laboratory, 120 David L Boren Blvd, Norman, OK, USA, 73072.]

The concepts of evaporation and precipitation as related to relative humidity have evolved from a mechanistic paradigm (air and water particles showing macroscopic characteristics), to a saturation paradigm (water vapor dissolving in air up to a maximum value; air showing saturation capacity), to the correct kinetic model (evaporation and condensation as a dynamic equilibrium, Dalton's law of partial pressure, Bernoulli's Kinetic theory of gases). Unfortunately, most of the nomenclature on relative humidity, evaporation, condensation, and precipitation was coined during the saturation paradigm period and persists, even though more correct terminology exists (equilibrium vapor pressure instead of saturation point, for instance).

The incorrect concept of saturation with respect to relative humidity is very pervasive. Unlike other science misconceptions that are acquired by people through their daily experiences, their own environment explorations, their social interactions, and media, this misconception is also formally taught. Regardless of its origin, scientific misconceptions are tenacious and very resistant to change, mostly because unlearning is extremely difficult if the information "makes sense" from an uninformed or simplistic viewpoint. Because no research has tried to determine the extent of misconceptions about relative humidity, this study aims to contribute to the science education literature in this important area.

The purpose of this paper is to investigate college students' knowledge of the concept of relative humidity by (1) documenting current student ideas about relative humidity, (2) detecting what misconceptions students have about relative humidity and related areas such as evaporation, condensation, and precipitation, and (3) providing evidence that the questionnaire used for data collection is valid and reliable. The research design included the use of a locally-designed, multiple-choice survey to collect information on students' concepts of relative humidity, evaporation, condensation, and precipitation before the topic is covered in class. The participants were enrolled at OU's METR 1014 class during the Fall 2005 semester.

Available online at http://cimms.ou.edu/~ladue/Papers/fredrickson-ams06.pdf#search=%22fredrickson%20humidity%20students%20%22what%20do%22%22.

Friedrich, K., U. Germann, J. J. Gourley, P. Tabary, 2007: Effects of radar beam shielding on rainfall estimation for polarimetric C-band radar. Journal of Atmospheric and Oceanic Technology, 24, 1839-1859.

Fritz, A., V. Lakshmanan, T. M. Smith, E. Forren, B. Clarke, 2006: A validation of radar reflectivity control methods. Preprints, 22nd Conference on Interactive Information Processing Systems, Atlanta, GA, USA, AMS, CD-ROM, 9.10.

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_102136.htm.

Galletti, M., D. Zrnic, D. Doviak, G. Zhang, J. Crain, 2010: Polarimetric phased array weather radar: Concepts for Polarimetric Calibration. Preprints, 2010 International Symposium on Phased Array Systems and Technology (ARRAY), Boston, MA, USA, IEEE, 387-393.

Available online at http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5613340&tag=1.

Galletti, M., D. S. Zrnic, 2011: Bias in copolar correlation coefficient caused by antenna radiation patterns. IEEE Transections on Geoscience and Remote Sensing, 49, 2274-2284.

We present a theoretical study of the bias in the copolar correlation coefficient caused by cross-polar radiation patterns and by unmatched horizontal and vertical copolar radiation patterns. The analysis of the bias induced by cross-polarization radiation is carried out for both modes of operation of polarimetric radars, designated as the simultaneous transmission and reception of horizontally and vertically polarized waves and the alternate transmission of horizontally and vertically polarized waves, respectively. The bias caused by unmatched horizontal and vertical copolar radiation patterns as a function of slight differences in pointing angles and beamwidths is also analyzed. In well-designed weather radars, for the purpose of hydrometeor classification, the overall acceptable bias in the copolar correlation coefficient should be less than about 0.01. The levels of cross-to-copolar gain ratios for acceptable performance are indicated. Ultimately, pointing angle and beamwidth tolerances are indicated for horizontal and vertical copolar antenna patterns.

Galletti, M., D. S. Zrnic, V. M. Melnikov, R. J. Doviak, 2012: Degree of Polarization at Horizontal Transmit: Theory and Applications for Weather Radar.. IEEE Transactions on Geoscience and Remote Sensing, 50, 1291-1301.

This paper considers weather radar measurements at linear depolarization ratio (LDR) mode, consisting of transmission of horizontal polarization and simultaneous reception of the copolar (horizontal) and cross-polar (vertical) components of the returned wave. Such a system yields the coherency matrix, with four degrees of freedom. After a theoretical analysis of its structure and symmetries, we focus on three cross-polarization variables: LDR, cross-polar correlation coefficient at horizontal transmit (ρxh), and degree of polarization at horizontal transmit (pH). The different properties of these variables with respect to backscattering and propagation are analyzed, together with the bias induced by antenna cross-channel coupling. It is demonstrated that the degree of polarization at horizontal transmit possesses attractive properties in terms of robustness to propagation effects and antenna cross-channel coupling.

Gao, J., M. Xue, S. Lee, A. Shapiro, Q. Xu, K. K. Droegemeier, 2006: A three-dimensional variational single-doppler velocity retrieval method with simple conservation equation constraint. Meteorol. Atmos. Phys., 94, 11-26.

Gao, J., D. J. Stensrud, T. M. Smith, K. Manross, J. Brogden, K. Kuhlman, 2011: A Realtime Weather-Adaptive 3DVAR Analysis System with Automatic Storm Positioning and On-demand Capability. Extended Abstracts, 35th Conference on Radar Meteorology, Denver, CO, USA, AMS, 115.

Radar is a fundamental tool for severe storm monitoring and nowcasting activities. Forecasters examine real-time NEXRAD observations from multiple radars, other remote sensing tools, severe weather detection algorithms, and use their considerable experience and situational awareness to issue severe storm warnings that help protect the public from hazardous weather events. However, escalating data flow rates from new sensors and applications will make it challenging for forecasters to make the best use of all the available data in warning operations in a timely manner. To overcome this difficulty, a real-time, weather-adaptive three-dimensional variational data assimilation (3DVAR) system has been developed recently for NOAA supported Warn-on-Forecast project (WoF) to incorporate all available traditional and radar observations within an analysis domain that could be hit by severe weather, including tornadoes, hails and strong damage winds. The unique features include: (1) The system has the ability to automatically detect and analyze severe local hazardous weather events at 1km horizontal resolution every 5 minutes. (2) The analysis can also be performed with on-demand capability in which end-users (or forecasters) set up the location of the analysis domain in real time based on the current weather situation. (3) The analysis product can help forecasters identify strong circulations imbedded in thunderstorms so that the accuracy of warnings for hazardous weather threats may be improved Although still in the early development stage, the system performed very well during the spring of 2010. Many severe weather events were all successfully detected and analyzed. Currently, we are working to make the analysis product available in "near realtime" (4-5 minutes delay) to the NWS forecasters as one of the official projects of the NOAA's HWT Experimental Warning Program. The objectivity of the procedure ensures that (i) all available information, including all nearby WSR-88Ds and NAM high resolution analysis and forecast products, are used, (ii) physically-consistent gridded data are provided to forecasters to help make their warning decisions in a timely manner, and (iii) the problem of subjectivity, inherent to some arbitrary criteria in some severe weather detection algorithms, is avoided. The performance of the system during the 2011 Spring season experiment will be reported during the conference.

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper191834.html.

Giangrande, S. E., A. V. Ryzhkov, 2005: Calibration of Dual-Polarization Radar in the Presence of Partial Beam Blockage. Journal of Atmospheric and Oceanic Technology, 22, 1156-1166.

Giangrande, S. E., A. V. Ryzhkov, J. Krause, 2005: Automatic Detection of the Melting Layer with a Polarimetric Prototype of the WSR-88D Radar. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, 11R.2.

Giangrande, S. E., A. V. Ryzhkov, 2007: Estimation of rainfall based on the results of polarimetric echo classification. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P6B.7.

Giangrande, S., J. Krause, A. Ryzhkov, 2008: Automatic designation of the melting layer with a polarimetric prototype of the WSR-88D radar. Journal of Applied Meteorology and Climatology, 47, 1354-1364.

Giangrande, S., A. Ryzhkov, 2008: Estimation of rainfall based on the results of polarimetric echo classification. Journal of Applied Meteorology and Climatology, 47, 2445-2462.

Godfrey, C. M., D. J. Stensrud, L. M. Leslie, 2005: The influence of improved land surface and soil data on mesoscale model predictions. Proc. 19th Conference on Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 4.7.

One of the most difficult aspects in the evaluation of land surface models is the lack of observational data for accurate specification of the model initial conditions. Routine observations of fractional vegetation coverage and leaf area index (LAI) are not available at high resolution (~1 km), nor are observations of soil moisture and soil temperature. This gap in our observational capabilities seriously hampers the evaluation and improvement of land surface model parameterizations, since model errors may be related to improper initial conditions as much as to inaccuracies in the model formulations. To overcome these difficulties, two unique data sets are used. First, fractional vegetation coverage and LAI are derived from biweekly maximum normalized difference vegetation index (NDVI) composites at 1 km resolution obtained from daily observations by the Advanced Very High Resolution Radiometer (AVHRR) onboard National Oceanic and Atmospheric Administration satellites. Second, the Oklahoma Mesonet measures soil moisture and soil temperature at 15-minute intervals. Combined, these two data sets provide significantly improved initial conditions for land surface models and allow us to evaluate the utility of the land surface models with much greater confidence and detail than previously.

The value of these two data sources to land surface model initializations is evaluated using the Penn State-NCAR fifth-generation Mesoscale Model (MM5). Forecasts that both include and neglect these unique land surface observations are compared. Results are verified against the dense network of surface observations afforded by the Oklahoma Mesonet, including surface flux data derived from special sensors available at some of the Mesonet sites. Implications for further data requirements are discussed.

Godfrey, C. M., D. J. Stensrud, L. M. Leslie, 2006: Soil temperature and moisture errors in Eta model analyses. Proc. 20th Conf. on Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, JP1.2.

Forecast models require accurate soil temperature and soil moisture conditions to be able to properly partition the surface heat fluxes that drive the evolution of the planetary boundary layer. The National Centers for Environmental Prediction (NCEP) operational Eta model produces land surface analyses by continuously cycling soil temperature and moisture fields. In the past, these fields evolved only in response to radiation budget constraints and modeled precipitation, but NCEP recently upgraded the self-cycling process to assimilate observed precipitation. This study highlights potential problems with the land surface analysis from the Eta model by comparing 00 UTC and 12 UTC Eta model analyses of soil temperature and moisture at several depths with observations from the Oklahoma Mesonet. There are strong biases in soil temperature and there is a severe underestimation of soil moisture at all depths. There is notable improvement in the analyzed soil moisture fields after the change to a new assimilation scheme. While this change reduced the magnitude of the errors, a strong dry bias persists in the soil moisture field. A simple one-layer slab soil model reveals that these soil moisture errors alone may account for 1.0-1.5 degrees Celsius increases in maximum soil temperatures during the day and reductions in soil temperatures at night of 0.3-0.8 degrees Celsius. The remaining soil temperature errors likely stem from documented problems with the solar radiation and longwave parameterizations within the Eta model.

Available online at http://www.cimms.ou.edu/~cgodfrey/landsfc/.

Gourley, J. J., P. Tabary, J. Parent-du-Chatelet, 2006: Data quality of the Meteo-France C-band polarimetric radar. Journal of Atmospheric and Oceanic Technology, 23, 1340-1356.

Gourley, J. J., P. Tabary, J. Parent-du-Chatelet, 2007: Empirical estimation of attenuation from differential propagation phase measurements at C-band. Journal of Applied Meteorology and Climatology, 46, 306-317.

Gourley, J. J., P. Tabary, J. Parent-du-Chatelet, 2007: A fuzzy logic algorithm for the separation of precipitating from non-precipitating echoes using polarimetric radar observations. Journal of Atmospheric and Oceanic Technology, 24, 1439-1451.

Gourley, J. J., Z. L. Flamig, Y. Hong, T. J. Schuur, S. Giangrande, J. A. Vrugt, 2009: Hydrologic Performance of Rainfall Estimates from Polarimetric Radar. Proc. 34th Conference on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, P14.18.

Gourley, J. J., S. E. Giangrande, Y. Hong, Z. L. Flamig, T. J. Schuur, J. A. Vrugt, 2010: Impacts of polarimetric radar observations on hydrologic simulation. J. Hydrometeor., 11, 781-796.

Green, J. S., V. Lakshmanan, T. M. Smith, 2005: Quantitative analysis of different methods for merging radar reflectivity data. Preprints, 4th Student conference, San Diego, CA, USA, AMS, CD-ROM, P1.13.

Gu, J. Y., A. V. Ryzhkov, P. Zhang, P. Neilley, M. Knight, B. Wolf, D. I. Lee, 2011: Polarimetric attenuation correction in heavy rain at C band. Journal of Applied Meteorology and Climatology, 50, 39-58.

Guillot, E. M., V. Lakshmanan, T. M. Smith, G. J. Stumpf, D. W. Burgess, K. L. Elmore, 2008: Tornado and Severe Thunderstorm Warning Forecast Skill and its Relationship to Storm Type. Extended Abstracts, 23rd Conference on Interactive Information Processing Systems, New Orleans, LA, USA, AMS, 4A.3.

The amount of forecast skill involved when issuing tornado and severe thunderstorm warnings is closely related to the type of storm that causes the severe weather. Storms from eight tornado outbreaks are classified and correlated with tornado warnings and severe thunderstorm warnings. These warnings were verified, missed, or shown to be false alarms by relating them with storm reports that match temporally and spatially with those in the Storm Prediction Center's database. Certain forecast parameters, including the critical success index (CSI), probability of detection (POD), false alarm ratio (FAR), and warning lead time are calculated for each storm type and for each type of warning. Because it was not practical to manually classify these storms (~50,000 entities), a decision tree was trained on a subset of manually classified storms using Quinlan's C4.5 algorithm. The decision tree was then used to automatically classify storms as being of one of four types: supercellular, linear, pulse or unorganized. It was found that both tornado warnings and severe thunderstorm warnings issued for isolated supercells and convective line storms have higher CSI, higher POD, and lower FAR scores than those issued for pulse and non-organized storms. Lead times were consistently longer for supercell and line storms, while usually very short for pulse and non-organized storms. We conclude that measures of forecast skill are particularly sensitive to the type of storm. Thus, any measurement of forecast skill, such as the year-over-year skill measure of an individual forecast office, has to take into account the types of storms in that office's warning area in the time period considered.

Available online at http://ams.confex.com/ams/88Annual/techprogram/paper_132244.htm.

Hamill, T. M., R. Schneider, H. E. Brooks, G. Forbes, H. B. Bluestein, M. Steinberg, D. Melendez, R. M. Dole, 2005: The May 2003 extended tornado outbreak. Bulletin of the American Meteorological Society, 86, 531-542.

In May 2003 there was a very destructive extended outbreak of tornadoes across the central and eastern United States. More than a dozen tornadoes struck each day from 3 May to 11 May 2003. This outbreak caused 41 fatalities, 642 injuries, and approximately $829 million dollars of property damage. The outbreak set a record for most tornadoes ever reported in a week (334 between 4-10 May), and strong tornadoes (F2 or greater) occurred in an unbroken sequence of nine straight days. Fortunately, despite this being one of the largest extended outbreaks of tornadoes on record, it did not cause as many fatalities as in the few comparable past outbreaks, due in large measure to the warning efforts of National Weather Service, television, and private-company forecasters and the smaller number of violent (F4-F5) tornadoes. This event was also relatively predictable; the onset of the outbreak was forecast skillfully many days in advance.

An unusually persistent upper-level trough in the intermountain west and sustained low-level southerly winds through the southern Great Plains produced the extended period of tornado-favorable conditions. Three other extended outbreaks in the past 88 years were statistically comparable to this outbreak, and two short-duration events (Palm Sunday 1965 and the 1974 Superoutbreak) were comparable in the overall number of strong tornadoes. An analysis of tornado statistics and environmental conditions indicates that extended outbreaks of this character occur roughly every 10 to 100 years.

Hane, C. E., D. L. Andra, Jr., J. A. Haynes, T. E. Thompson, F. H. Carr, 2005: On the Importance of Environmental Factors in Influencing the Evolution of Morning Great Plains MCS Activity during the Warm Season. Extended Abstracts, Eleventh Conference on Mesoscale Processes, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P3M.6.

Hansen, T. L., T. J. LeFebvre, C. S. Bullock, J. Wakefield, J. Ramer, S. Williams, G. J. Stumpf, K. Scharfenberg, J. T. Ferree, B. C. Motta, E. Gruntfest, S. Romano, M. K. Zappa, W. F. Roberts, 2010: Hazard Information Services Vision. Extended Abstracts, 26th Conf. on Interactive Information and Processing Systems, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 6B.4.

Currently, National Weather Service forecasters use three separate software tools to issue warnings: WarnGen for short-fused hazards, the Graphical Hazards Generator for long-fused hazards, and RiverPro for hydrological hazards. Hazard Information Services (formerly called The Next Generation Warning Tool -- NGWT) is a challenging endeavor which seeks to integrate these disparate tools while simultaneously transitioning the National Weather Service (NWS) Hazard Program from a paradigm of issuing products to one of decision support. In October 2009, a workshop was attended by the diverse set of stakeholders in this enterprise -- end users (emergency managers, private sector), social scientists (WAS*IS / SSWIM members), operational weather forecasters, software designers and developers, and program managers from diverse organizations across NOAA and the private sector. There is innovation and challenge in bringing all stakeholders together in one room to represent each of their interests; the scope is broad, but the reward is a design that encompasses the full range of requirements. The goals of the workshop were to refine the set of requirements and design as well as foster social learning through group problem-solving with the full spectrum of stakeholders. Understanding and appreciating all viewpoints will provide a foundation for success. We will present the resulting design and vision.

Harasti, P. R., D. Smalley, M. Weber, C. Kessinger, Q. Xu, P. Zhang, S. Liu, T. Tsui, J. Cook, Q. Zhao, 2005: On the development of a multi-algorithm radar data quality control system at the naval research laboratory. 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, XXXX.

Heinselman, P. L., A. Rowe, 2005: Estimating hail size using polarimetric radar. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, Amer. Meteor. Soc., CD-ROM, P9R.16.

Heinselman, P. L., D. M. Schultz, 2006: Intraseasonal variability of summertime storms over central Arizona during 1997 and 1999. Weather and Forecasting, 21, 559-578.

Although previous climatologies over central Arizona show a summer diurnal precipitation cycle, on any given day precipitation may differ dramatically from this climatology. The purpose of this study is to investigate the intraseasonal variability of diurnal storm development over Arizona and explore the relationship to the synoptic-scale flow and Phoenix soundings during the 1997 and 1999 North American Monsoons (NAMs). Radar reflectivity mosaics constructed from Phoenix and Flagstaff Weather Surveillance Radar-1988 Doppler (WSR-88D) reflectivity data reveal six repeated storm development patterns or regimes. The diurnal evolution of each regime is illustrated by computing frequency maps of reflectivity 25 dBZ and greater during 3-h periods. These regimes are named to reflect their regional and temporal characteristics: dry regime (DR), Eastern Mountain regime (EMR), Central–Eastern Mountain regime (CEMR), Central–Eastern Mountain and Sonoran-isolated regime (CEMSIR), Central–Eastern Mountain and Sonoran regime (CEMSR), and nondiurnal regime (NDR).
Composites constructed from the National Center for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) Reanalysis Project data show that regime occurrence is related to the north–south location of the 500-hPa geopotential height ridge axis of the Bermuda High and the east–west location of the 500-hPa monsoon boundary, a boundary between dry air to the west and moist air to the east. Consequently, precipitable water (PW) from 1200 UTC Phoenix soundings is the best parameter for discriminating the six regimes.

Heinselman, P. L., A. V. Ryzhkov, 2006: Validation of Polarimetric Hail Detection. Weather and Forecasting, 21, 839-850.

This study describes, illustrates, and validates hail detection by a simplified version of the National Severe Storms Laboratory's (NSSL) fuzzy logic polarimetric hydrometeor classification algorithm (HCA). The HCA uses four radar variables: reflectivity, differential reflectivity, cross-correlation coefficient, and "reflectivity texture" to classify echoes as rain mixed with hail, ground clutter-anomalous propagation, biological scatterers (insects, birds, and bats), big drops, light rain, moderate rain, and heavy rain. Diagnostic capabilities of HCA, such as detection of hail, are illustrated for a variety of storm environments using polarimetric radar data collected mostly during the Joint Polarimetric Experiment (JPOLE; 28 April-13 June 2003).

Hail classification with the HCA is validated using 47 rain and hail reports collected by storm-intercept teams during JPOLE. For comparison purposes, probability of hail output from the Next-Generation Weather Radar (NEXRAD) Hail Detection Algorithm (HDA) is validated using the same ground truth. The anticipated polarimetric upgrade of the Weather Surveillance Radar-1988 Doppler (WSR-88D) network drives this direct comparison of performance. For the four examined cases, contingency table statistics show that the HCA outperforms the HDA. The superior performance of the HCA results primary from the algorithm's lack of false alarms compared to the HDA. Statistical significance testing via bootstrapping indicates that differences in POD and CSI between the algorithms are statistically significant at the 95% confidence level, whereas differences in FAR and HSS are statistically significant at the 90% confidence level.

Heinselman, P. L., D. L. Priegnitz, K. L. Manross, R. Adams, 2006: Comparison of storm evolution characteristics: The NWRT and WSR-88D. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, AMS, CD-ROM, 14.1.

The National Weather Research Testbed (NWRT), located in Norman, Oklahoma at the National Severe Storms Laboratory, began collecting data with the Phased Array Radar (PAR) in spring of 2003. Until recently, these data were used mostly to address engineering issues. During the late spring of 2006 the stability of the NWRT PAR was sufficient to allow the collection of data on several storm events. A key advantage of the NWRT is the capability to adaptively scan storms at higher temporal resolution than is possible by the WSR-88D (1 min or less vs 5 min, respectively). Benefits of faster scanning of convective storms include better understanding of storm dynamics and initiation, better detection of small-scale phenomena, and increased lead time for warnings, to name a few. This paper marks the beginning of a series of studies that seek to improve understanding of the evolution of small-scale phenomena, like tornadoes and microbursts, as well as the development of convective storm structure. A first step toward this goal is comparative analysis of the evolution of convective storm structure for single cells, multicells, supercells, and line segments using rapid-scanning reflectivity and velocity data collected by the NWRT and conventional reflectivity data collected by the nearby WSR-88D (KTLX) during May and June 2006. The analysis will focus on features associated with storm initiation, growth, and decay, including mergers and hail cores. Results of this analysis will be reported in the extended abstract.

Heinselman, P. L., D. Priegnitz, T. Smith, D. Andra, R. Palmer, M. Biggerstaff, 2007: Spring 2007 National Weather Radar Testbed Demonstration. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P5.7.

Although WSR-88D data are indispensable for assessing storm severity, a recent comparative analysis of the evolution of several severe convective storms using data collected by KLTX (Oklahoma City, OK) WSR-88D and the National Weather Radar Testbed (NWRT) phased array radar (PAR) demonstrated the ability of PAR to provide the high-temporal resolution data needed for early detection of significant storm development, hail signatures, gust fronts, and wind shear. These high-temporal resolution data have the potential to benefit short-term forecasting and warning decision-making, though users may be challenged by the rapid influx of data.

This spring, National Weather Service forecasters participating in the NWRT demonstration at the NOAA Hazardous Weather Testbed in Norman, Oklahoma will be introduced to PAR data for the first time. The NWRT demonstration will be conducted from 15 April through 30 June 2007 and will primarily be concerned with data collection within a 150 km radius of the PAR prior to and during severe weather warning operations. Two overarching goals of the NWRT demonstration are to test the adaptive, multi-purpose scanning capability of PAR and to collect feedback from NWS forecasters on operational benefits and challenges of integrating PAR data into warning decision-making. The preliminary results of this study will be reported in the extended abstract.

Available online at http://ams.confex.com/ams/pdfpapers/123058.pdf.

Heinselman, P. L., D. Priegnitz, K. Manross, R. Adams, 2007: Comparison of Storm Evolution Characteristics: The NWRT and WSR-88D. Preprints, 23rd Conference on Interactive Information and Processing Systems, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 7.5. [Available from Pam Heinselman, 120 David L Boren Blvd, Norman, OK, USA, 73069.]

The National Weather Radar Testbed (NWRT), located in Norman, Oklahoma at the National Severe Storms Laboratory, began collecting data with the Phased Array Radar (PAR) in spring of 2003. Until recently, these data were used mostly to address engineering issues. Beginning in late spring of 2006 the stability of the NWRT PAR was sufficient to allow the collection of data. Several storm eventshave been captured since colletion began, and more atmospheric phenomena are being added to the PAR data set. A key advantage of the NWRT is the capability to adaptively scan storms at higher temporal resolution than is possible by the WSR-88D (1 min or less vs 5 min, respectively). Benefits of faster scanning of convective storms include better understanding of storm dynamics and initiation, better detection of small-scale phenomena, and increased lead time for warnings, to name a few. This paper marks the beginning of a series of studies that seek to improve understanding of the evolution of small-scale phenomena, like tornadoes and microbursts, as well as the development of convective storm structure. A first step toward this goal is comparative analysis of the evolution of convective storm structure for single cells, multicells, and line segments using rapid-scanning reflectivity and velocity data collected by the NWRT and conventional reflectivity data collected by the nearby WSR-88D (KTLX) during May and June 2006. The analysis will focus on features associated with storm initiation, growth, and decay, including mergers and hail cores. Results of this analysis will be reported in the extended abstract.

Heinselman, P. L., D. Priegnitz, T. Smith, D. Andra, R. Palmer, M. Biggerstaff, 2007: Spring 2007 National Weather Radar Testbed Demonstration. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, American Meteorological Society, CD-ROM, P5.7.

Available online at http://ams.confex.com/ams/33Radar/techprogram/paper_123058.htm.

Heinselman, P. L., D. Priegnitz, K. Manross, R. Adams, 2007: Comparison of Storm Evolution Characteristics: The NWRT and WSR-88D. Preprints, 23rd Conference on 23rd Conference onInteractive Information and Processing Systems, San Antonio, TX, USA, Amer. Meteor. Soc., CD-ROM, 7.8.

Heinselman, P., S. Weiss, M. Coniglio, D. Andra, G. Stumpf, B. Phillips, J. Brotzge, cited 2008: 2008 Spring HWT Experiments at the NWC. [Available online at ://http://www.nwas.org/newsletters/pdf/news_october2008.pdf.]

Heinselman, P., cited 2007: National symposium on latest developments in multifunction phased array radar.. [Available online at ://http://www.nwas.org/newsletters/pdf/news_dec2007.pdf.]

Heinselman, P. L., B. L. Cheong, R. D. Palmer, D. Bodine, K. Hondl, 2008: Radar refractivity retrievals from KTLX: Insights into operational benefits and limitations. Report of the National Severe Storms Laboratory ., 32 pp.

Heinselman, P. L., B. L. Cheong, R. D. Palmer, D. Bodine, K. Hondl, 2007: Real-time implementation of refractivity retrievals at the Norman Weather Forecast Office. Report of the National Severe Storms Laboratory ., 23 pp.

Heinselman, P. L., D. L. Priegnitz, K. L. Manross, T. M. Smith, R. W. Adams, 2008: Rapid sampling of severe storms by the National Weather Radar Testbed Phased Array Radar. Weather and Forecasting, 23, 808-824.

A key advantage of the National Weather Radar Testbed Phased Array Radar (hereafter, PAR) is the capability to adaptively scan storms at higher temporal resolution than is possible with the Weather Surveillance Radar-1988 Doppler (WSR-88D): 1 min or less vs 4.1 min, respectively. High-temporal resolution volumetric radar data is a necessity for rapid identification and confirmation of weather phenomena that can develop within minutes. The purpose of this paper is to demonstrate the PAR’s ability to collect rapid-scan volumetric data that provide more detailed depictions of quickly evolving storm structures than the WSR-88D. Scientific advantages of higher-temporal resolution PAR data are examined for three convective storms that occurred during the spring and summer of 2006, including a reintensifying supercell, a microburst, and a hail storm. The analysis of the reintensifying supercell (58 s updates) illustrates the capability to diagnose the detailed evolution of developing and/or intensifying areas of 1) low-altitude divergence and rotation and 2) rotation through the depth of the storm. The fuller sampling of the microburst’s storm life cycle (34 s updates) depicts precursors to the strong surface outflow that are essentially indiscernible in the WSR-88D data. Furthermore, the 34 s scans provide a more precise sampling of peak outflow. The more frequent sampling of the hail storm (26 s updates) illustrates the opportunity to analyze storm structures indicative of rapid intensification, the development of hail aloft, and the onset of the downdraft near the surface.

Heinselman, P. L., 2008: Spring 2008 Real-time Phased Array Radar Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, P13.2. [Available from Pam Heinselman, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Although WSR-88D data are indispensable for assessing storm severity, a recent comparative analysis of the evolution of several severe convective storms using data collected by the KLTX (Oklahoma City, OK) WSR-88D and the National Weather Radar Testbed (NWRT) Phased Array Radar (PAR) in Norman, Oklahoma demonstrated the ability of PAR to sample the temporal evolution of significant storm development, hail signatures, gust fronts, and wind shear in more detail. These high-temporal resolution data have the potential to benefit short-term forecasting and warning decision-making, though users may be challenged by the rapid influx of data.

This spring, National Weather Service forecasters participating in the Real-time Phased Array Radar Experiment at the NOAA Hazardous Weather Testbed in Norman, Oklahoma were introduced to PAR data and asked to evaluate its utility for severe weather warning operations in both real-time operations and simulated real-time playback of two archived weather events. During the six-week experiment (28 April through 6 June 2008) 27 participants evaluated the following four aspects of weather surveillance with the PAR: 1) strengths and limitations of PAR data,compared to the WSR-88D, in the analysis of severe storms, 2) how characteristics of PAR scan strategies affect the interpretation of severe storms, 3) how PAR data affects warning decision making, and 4) how PAR data may be of benefit to operational responsibilities. The results of this study will be reported in the extended abstract.

Available online at http://ams.confex.com/ams/pdfpapers/141605.pdf.

Heinselman, P. L., D. J. Stensrud, R. M. Hluchan, P. L. Spencer, P. C. Burke, K. L. Elmore, 2009: Radar reflectivity-based estimates of mixed-layer depth. Journal of Atmospheric and Oceanic Technology, 26, 229-239.

This study investigates the potential for estimating mixed-layer depth by taking advantage of the radial gradients in the radar reflectivity field produced by the large vertical gradients in water vapor mixing ratio that are characteristic of the mixing height. During the day, this relationship often results in a ring of maximum reflectivity observed to progress radially outward from the radar as mixed-layer depth increases. A comparison of mixed-layer depths estimated from the Oklahoma City WSR-88D (KTLX) with those estimated from a nearby 915 MHz profiler reveals that mixed-layer depths from the WSR-88D are slightly too high (up to 0.3 km) during the first three hours of the diurnal cycle, nearly unbiased midday, and slightly too low (0.2 km or less) thereafter. The procedure estimates mixed-layer depths only during the daytime hours from 1300–2300 UTC. The weather conditions for the 17 days studied were fairly quiescent, with sunny skies and light winds.

Heinselman, P. L., S. Torres, R. Adams, C. D. Curtis, E. Forren, I. R. Ivic, D. Priegnitz, J. Thompson, D. A. Warde, 2009: Phased array radar innovative sensing experiment. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P6.5A.

Heinselman, P. L., B. L. Cheong, R. D. Palmer, D. Bodine, K. Hondl, 2009: Radar refractivity from KTLX: Insights into operational benefits and limitations. Preprints, 25th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., P1.26.

Heinselman, P. L., T. M. Smith, K. L. Ortega, K. Manross, 2009: Radar sampling of low-altitude circulations by phased array radar. Preprints, 25th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., 9B.4.

Heinselman, P. L., 2009: Spring 2008 phased array radar experiment. Preprints, 25th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Phoenx, AZ, USA, Amer. Meteor. Soc., 9B.5.

Heinselman, P. L., B. L. Cheong, R. D. Palmer, D. Bodine, K. Hondl, 2009: Radar Refractivity Retrievals in Oklahoma: Insights into Operational Benefits and Limitations. Weather and Forecasting, 24, 1345-1361.

The 2007 and 2008 spring refractivity experiments at KTLX investigated the potential utility of high-resolution, near-surface refractivity measurements to operational forecasting. During these experiments, forecasters at the Norman, Oklahoma, National Weather Service Forecast Office (NWSFO) assessed refractivity and scan-to-scan refractivity change fields retrieved from the Weather Surveillance Radar-1988 Doppler weather radar near Oklahoma City—Twin Lakes, Oklahoma (KTLX). Both quantitative and qualitative analysis methods were used to analyze the 41 responses from seven forecasters to a questionnaire designed to measure the impact of refractivity fields on forecast operations. The analysis revealed that forecasts benefited from the refractivity fields on 25% of the days included in the evaluation. In each of these cases, the refractivity fields provided complementary information that somewhat enhanced the forecasters’ capability to analyze the near-surface environment and boosted their confidence in moisture trends. A case in point was the ability to track a retreating dryline after its location was obscured by a weak reflectivity bloom caused by biological scatterers. Forecasters unanimously agreed, however, that the impact of this complementary information on their forecasts was too insignificant to justify its addition as an operational dataset. The applicability of these findings to other NWSFOs may be limited to locations with similar weather situations and access to surface data networks like the Oklahoma Mesonet.

Heinselman, P. L., S. M. Torres, 2010: Exploiting NWRT capabilities to improve temporal data resolution.. Extended Abstracts, 26th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., 15.B.2.

Faster scanning of hazardous weather with radar is a primary need of users. This need is exemplified by the implementation of faster volume coverage patterns (e.g., VCP 12) by the National Weather Service, responses to studies of user needs, and reports by the National Research Council. Traditional VCPs modified to provide faster updates require trade-offs such as data quality and/or spatial resolution.

The electronic steering of the National Weather Radar Testbed Phased Array Radar (NWRT PAR) is capable of collecting higher temporal resolution data without some of the limitations of mechanically scanning radars. Most importantly, electronic steering allows scanning focused solely on areas of interest without having to collect data contiguously. This capability, termed adaptive scanning, produces higher temporal resolution data through more efficient use of radar resources.

This paper describes the technical PAR capabilities, software improvements, and scanning strategy developments that have led to the advancement of a SPY-1A antenna from a military-surveillance radar to a weather-surveillance radar with basic adaptive scanning capability. Individual weather events sampled by the NWRT PAR illustrate the evolution of high-temporal sampling capabilities of the NWRT PAR since spring 2007. Future enhancements to improve current adaptive scanning capabilities are discussed.

Heinselman, P. L., S. M. Torres, D. LaDue, H. Lazrus, 2011: 2010 Phased-array radar innovative sensing experiment. Extended Abstracts, 27th Interactive Information Processing Systems, Seattle, WA, USA, Amer. Meteor. Soc., 12B.4.

The National Weather Radar Testbed phased-array radar (NWRT PAR) has unique electronic scanning capabilities for weather surveillance. A key objective of the 2010 Phased-Array Radar Innovative Sensing Experiment (PARISE) is the demonstration and testing of the radar's capability to produce efficient and effective rapid sampling of severe storms. Rapid sampling is achieved through the implementation of electronic adaptive scanning, range oversampling, and other techniques, over a 90-degree sector. At the same time, an enhanced depiction of storm structure is attained through dense vertical sampling (22 tilts) and 50% azimuthal oversampling. The high-quality, rapid update data collected in spring 2010 provides the opportunity to improve understanding of storm processes in bowing line segments, hail storms, and fast moving tornadic storms.

The social science-component of the 2010 PARISE engaged 12 forecasters from three regions of the National Weather Service in the analysis of NWRT PAR data and took place during the last three weeks of April 2010. The primary objective of this user-focused experiment is to build an understanding of potential operational impacts of higher-temporal resolution data on the warning decision process and warning lead time. To accomplish this objective, on Tuesday and Wednesday of each week the four participants received training on the NWRT PAR instrumentation and gained experience analyzing the data and issuing warnings using three playback events. The three events included a microburst, quasi-linear convective system, and isolated supercell. On Thursdays forecasters participated in day-long experiment for which NWRT PAR data for two cases were used with two different update times for each case: one with the full-temporal resolution data, and the other with WSR-88D-like temporal resolution data. The two events included a low-topped supercell that formed in a tropical environment and a supercell that formed in more of a traditional Southern Plains environment. Following each event, each team discussed their warning decision making process with their facilitators, and then met with the other team to compare and contrast their warning decision experiences. These debriefings produced a very rich dataset that illustrates possible impacts of higher-temporal resolution data on the warning decision making process and how NWRT PAR data may be eventually be introduced to the field.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper184192.html.

Heinselman, P. L., S. M. Torres, 2011: High-temporal-resolution capabilities of the National Weather Radar Testbed Phased-Array Radar. Journal of Applied Meteorology and Climatology, 50, 579-593.

Since 2007 the advancement of the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) hardware and software capabilities has been supporting the implementation of high-temporal-resolution (1 min) sampling. To achieve the increase in computational power and data archiving needs required for high-temporal-resolution sampling, the signal processor was upgraded to a scalable, Linux-based cluster with a distributed computing architecture. The development of electronic adaptive scanning, which can reduce update times by focusing data collection on significant weather, became possible through functionality added to the radar control interface and real-time controller. Signal processing techniques were implemented to address data quality issues, such as artifact removal and range-and-velocity ambiguity mitigation, absent from the NWRT PAR at its installation. The hardware and software advancements described above have made possible the development of conventional and electronic scanning capabilities that achieve high-temporal-resolution sampling. Those scanning capabilities are sector- and elevation-prioritized scanning, beam multiplexing, and electronic adaptive scanning. Each of these capabilities and related sampling trade-offs are explained and demonstrated through short case studies.

Hiers, N. C., A. McGovern, D. H. Rosendahl, R. A. Brown, K. K. Droegemeier, 2008: Using spatiotemporal relational data mining to identify the key parameters for anticipating rotation initiation in simulated supercell thunderstorms. Preprints, 6th Conference on Artificial Intelligence Applications to Environmental Science, New Orleans, LA, USA, American Meteorological Society, J2.3.

Higgins, W., D. Ahijevych, J. Amador, A. Barros, E. Berbery, E. Caetano, R. Carbone, P. Ciesielski, R. Cifelli, M. Cortez-Vazquez, A. Douglas, M. Douglas, G. Emmanuel, C. Fairall, D. Gochis, D. Gutzler, T. Jackson, R. Johnson, C. King, T. Lang, M. Lee, D. Lettenmaier, R. Lobato, V. Magaña, J. Meitin, K. Mo, S. Nesbitt, F. Ocampo-Torres, E. Pytlak, P. Rodgers, S. Rutledge, J. Schemm, S. Schubert, A. White, C. Williams, A. Wood, R. Zamora, C. Zhang, 2006: The NAME 2004 Field Campaign and Modeling Strategy. Bulletin of the American Meteorological Society, 87, 79-94.

Hluchan, R., P. L. Heinselman, 2009: Evolution of a tornadic supercell and its environment sampled by Phased Array Radar and Oklahoma City Micronet. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P6.5.

Hluchan, R., P. L. Heinselman, R. A. Brown, 2010: Evolution of a tornadic supercell and its environment sampled by the NWRT Phased array radar and Oklahoma City Micronet. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, Amer. Meteor. Soc., 15.2.

The National Weather Radar Testbed Phased Array Radar (NWRT PAR) sampled a cyclic, tornadic supercell on 10 February 2009 as it moved northeast across the western side of Oklahoma City. During its lifetime the storm moved over the Oklahoma City Micronet (OKCNET) and Oklahoma Mesonet stations. The rapid updates of the NWRT PAR and the highspatial and temporal resolution of the OKCNET, collected near a high–population center, make this a unique event. Low–level analyses of these data show the storm exhibited cyclic tornadogenesis; two cycles of the supercell were examined in this study. After the tornado associated with the first cycle lifted, a new circulation formed along a bulge in the rear flank gust front. During both cycles of the supercell, a number of small cells developed south of the supercell and merged with the storm. This study documents the evolution and characteristics of these cells as they merge with the main supercell. These mergers often disrupted the organization of the hook echo.

Available online at http://ams.confex.com/ams/25SLS/techprogram/paper_176091.htm.

Hoekstra, S., K. Klockow, R. Riley, J. Brotzge, H. Brooks, 2011: A Preliminary Look at the Social Perspective of Warn-on-Forecast: Preferred Tornado Warning Lead Time and the General Public's Perceptions of Weather Risks. Weather, Climate, and Society, 3, 128-140.

Tornado warnings are currently issued an average of 13 minutes in advance of a tornado (Golden and Adams 2000) and are based on a warn-on-detection paradigm (Erickson and Brooks 2006). However, computer model improvements may allow for a new warning paradigm, warn-on- forecast, to be established in the future (Stensrud et al. 2009). This would mean that tornado warnings could be issued one to two hours in advance, prior to storm initiation. In anticipation of the technological innovation, this study inquires whether the “warn-on-forecast” paradigm for tornado warnings may be preferred by the public (i.e., individuals and single families). Our sample is drawn from visitors to the National Weather Center in Norman, Oklahoma. During the summer and fall of 2009, surveys were distributed to 320 participants to assess their understanding and perception of weather risks and preferred tornado warning lead-time.

Responses were analyzed according to several different parameters including age, region of residency, educational level, number of children, and prior tornado experience. A majority of the respondents answered many of the weather risk questions correctly. They seemed to be familiar with tornado seasons; however, they were unaware of the relative number of fatalities caused by tornadoes and several additional weather phenomena each year in the United States. The preferred lead-time was 34.3 minutes according to average survey responses. This suggests that while the general public may currently prefer a longer average lead-time than the present system offers, the preference does not extend to the one to two hour time-frame theoretically offered by the warn-on-forecast system. When asked what they would do if given a one-hour lead-time, respondents reported that taking shelter was a lesser priority than when given a 15-minute leadtime, and fleeing the area became a slightly more popular alternative. A majority of respondents also reported the situation would feel less life threatening if given a one-hour lead-time. These results suggest that how the public responds to longer lead times may be complex and situationally-dependent, and further study must be conducted to ascertain the users for whom the longer lead-times would carry the most value. These results form the basis of an informative stated-preference approach to predicting public response to long (> 1 hour) warning lead times, using public understanding of the risks posed by severe weather events to contextualize leadtime demand.

Homar, V., D. J. Stensrud, J. J. Levit, D. R. Bright, 2006: Value of Human-Generated Perturbations in Short-Range Ensemble Forecasts of Severe Weather. Weather and Forecasting, 21, 347-363.

During the spring of 2003, the Storm Prediction Center, in partnership with the National Severe Storms Laboratory, conducted an experiment to explore the value of having operational severe weather forecasters involved in the generation of a short-range ensemble forecasting system. The idea was to create a customized ensemble to provide guidance on the severe weather threat over the following 48 h. The forecaster was asked to highlight structures of interest in the control run and, using an adjoint model, a set of perturbations was obtained and used to generate a 32-member fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) ensemble. The performance of this experimental ensemble is objectively evaluated and compared with other available forecasts (both deterministic and ensemble) using real-time severe weather reports and precipitation in the central and eastern parts of the continental United States. The experimental ensemble outperforms the operational forecasts considered in the study for episodes with moderate-to-high probability of severe weather occurrence and those with moderate probability of heavy precipitation. On the other hand, the experimental ensemble forecasts of low-probability severe weather and low precipitation amounts have less skill than the operational models, arguably due to the lack of global dispersion in a system designed to target the spread over specific areas of concern for severe weather. Results from an additional test ensemble constructed by combining automatic and manually perturbed members show the best results for numerical forecasts of severe weather for all probability values. While the value of human contribution in the numerical forecast is demonstrated, further research is needed to determine how to better use the skill and experience of the forecaster in the construction of short-range ensembles.

Hondl, K. D., V. Lakshmanan, T. M. Smith, G. J. Stumpf, 2007: Warning Decision Support System - Integrated Information (WDSS-II) Progress and Plans. Preprints, 23rd Conference on Interactive Information Processing Systems, San Antonio, TX, USA, AMS, CD-ROM, 6.3.

The Warning Decision Support System -- Integrated Information (WDSS-II) has been enhanced to support several new research and real-time efforts. The real-time ingest now includes Canadian radar data, the National Weather Radar Testbed (NWRT) Phased Array Radar (PAR), and the CASA X-band radar network being testing in Oklahoma.

New outputs include Grib2 files and a variety of georeferenced products covering the continental United States and capable of being displayed in GIS systems such as Google Earth.

New or improved algorithms include an improved WSR-88D reflectivity quality-control algorithm, improved azimuthal shear detection, a local-maximum feature tracker, and a faster real-time 3D multi-radar product creation. New experiments include an experimental warning program, real-time delivery of products to the Storm Prediction Center (SPC) and several National Weather Service (NWS) forecast offices and a real-time hail verification experiment.

The 3D base radar display is being configured as the Four-Dimensional Stormcell Investigator (FSI) and is currently being transferred to the National Weather Service AWIPS. Also, there are plans to transfer the multi-radar, multi-sensor applications, as well as some aspects of the infrastructure to the next generation AWIPS.

Available online at http://ams.confex.com/ams/pdfpapers/118556.pdf.

Hood, K., R. Palmer, S. Torres, 2009: Automatic detection of wind turbine clutter using Doppler spectral features. Extended Abstracts, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P10.1.

Hood, K., S. Torres, R. Palmer, 2010: Automatic detection of wind turbine clutter for weather radars. Journal of Atmospheric and Oceanic Technology, 27, 1868-1880.

Horgan, K. L., D. M. Schultz, R. H. Johns, S. F. Corfidi, J. E. Hales, 2006: A five-year climatology of elevated severe convective storms in the United States east of the Rocky Mountains. Preprints, Severe Local Storms Special Symposium, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, P1.22.

Available online at http://www.cimms.ou.edu/~schultz/papers/horganetal2006.pdf.

Horgan, K. L., D. M. Schultz, R. H. Johns, J. E. Hales, S. F. Corfidi, 2007: A five-year climatology of elevated severe convective storms in the United States east of the Rocky Mountains. Weather and Forecasting, 22, 1031-1044.

Ice, R. L., D. A. Warde, A. D. Free, R. D. Rhoton, D. S. Saxion, C. A. Ray, N. K. Patel, O. E. Boydstun, D. S. Berkowitz, J. N. Chrisman, J. C. Hubbert, C. J. Kessinger, M. Dixon, S. M. Torres, 2007: Optimizing clutter filtering in the WSR-88D. Preprints, 23rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, AMS, CD-ROM, P2.11.

Ice, R. L., R. D. Rhoton, J. C. Krause, D. S. Saxion, O. E. Boydstun, A. K. Heck, J. N. Chrisman, D. S. Berkowitz, W. D. Zittel, D. A. Warde, 2009: Automatic clutter mitigation in the WSR-88D, design, evaluation, and implementation. Preprints, 34th International Conference on Radar Meteorology, Willaimsburg, VA, USA, American Meteorological Society, CD-ROM, P5.3.

The WSR-88D Radar Operations Center (ROC) has qualified, integrated, and implemented a new method of automatically identifying and filtering areas of radar returns containing ground clutter. The Clutter Mitigation Decision (CMD) algorithm is the result of several years of development at the National Center for Atmospheric Research (NCAR) and is based on fuzzy logic analysis of several parameters. During the implementation, ROC and NCAR engineers and scientists refined the algorithm to enhance performance and allow for effective application in the WSR-88D. The algorithm is designed for efficient integration into the radar signal processor, employing available software features. For the initial implementation, the ROC team developed an effective system architecture, incorporating automatic clutter filter application for the lowest elevation scans where anomalously propagated clutter is a significant problem. The team also incorporated CMD into the off-line clutter map generation process. CMD was deployed on the WSR-88D network, beginning in the spring of 2009, in Software Build 11.0.

This paper discusses the algorithm evolution and performance, summarizes integration efforts, and documents the technical evaluation. The paper includes a discussion of future integration of polarimetric enhancements.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_155409.htm.

Ice, R., G. Cate, R. Saffle, D. Sirmans, D. Zrnic, S. Torres, D. Warde, J. Hubbert, 2010: A signal processing roadmap for NEXRAD. Preprints, 26th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, P2.8.

Isaac, G. A., P. Joe, M. Bailey, F. Boudala, E. Campos, S. G. Cober, C. Doyle, D. Forsyth, I. Gultepe, R. M. Rasmussen, T. Smith, R. E. Stewart, 2010: Cloud and precipitation physics- Vancouver 2010 Olympics. Extended Abstracts, 13th Conference on Cloud Physics, Portland, OR, USA, American Meteorological Society, 12.5.

Isaac, G. A., P. Joe, J. Mailhot, M. E. Bailey, S. . Belair, F. S. Boudala, M. Brugman, E. Campos, R. L. Carpenter, S. G. Cober, B. Denis, C. Doyle, D. E. Forsyth, I. Gultepe, T. Haiden, L. Huang, J. A. Milbrandt, R. Mo, R. M. Rasmussen, T. Smith, R. E. Stewart, D. Wang, 2010: Nowcasting winter weather in complex terrain - Experiences from SNOW-V10. Extended Abstracts, 14th Conference on Mountain Meteorology, Olympic, CA, USA, American Meteorological Society, 15.4.

Istok, M., M. Fresch, S. Smith, Z. Jing, R. Murnan, A. Ryzhkov, J. Krause, M. Jain, J. Ferree, P. Schlatter, B. Klein, D. Stein, G. Cate, R. Saffle, 2009: WSR-88D dual polarization initial operational capabilities. Extended Abstracts, 25th Conference on International Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, AMS, 15.5.

Ivic, I., A. Zahrai, S. Torres, 2005: Decorrelation in range of oversampled weather radar signals using FIR filter. Preprints, 32nd International Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, P4R.12.

Ivic, I. R., D. S. Zrnic, 2007: USE OF COHERENCY TO IMPROVE SIGNAL DETECTION IN DUAL-POLARIZATION WEATHER RADARS. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, National Weather Service (NWS), CD-ROM, P11B.14.

Currently the WSR-88D network of weather surveillance radars (i.e., NEXRAD) uses only power estimates for signal censoring. The planned network upgrade to dual polarization will result in 3dB SNR reduction because transmitter output will be split between H and V channels. As a result, this will diminish radar sensitivity if the current power based censoring scheme is retained. In this paper, an alternative signal detection scheme is proposed which yields the improved detection over current approach. It mitigates the effects of SNR decrease by utilizing the weather signal coherency in sample-time and across channels.

Available online at http://ams.confex.com/ams/33Radar/techprogram/paper_123063.htm.

Ivic, I. R., D. S. Zrnic, 2008: Optimizing Coherency Approach to Improve Signal Detection in Dual-polarization Weather Radars. Proc. 5th European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Cooperative Institute for Mesoscale Meteorological Studies (CIMM, CD-ROM, 9.7. [Available from Igor Ivic, 120 David L Boren Blvd, Norman, OK, USA, 73072.]

Currently the WSR-88D network of weather surveillance radars (i.e., NEXRAD) uses only power estimates for signal censoring. The planned network upgrade to dual polarization will result in 3dB SNR reduction because transmitter output will be split between H and V channels. As a result, this will diminish radar sensitivity if the current signal-to-noise ratio (SNR) based censoring scheme is retained. An alternative signal detection scheme has been proposed which yields improved detection over the current approach. It mitigates the effects of SNR decrease by utilizing the weather signal coherency in sample-time and across channels. It does so by summing the estimates of powers and autocorrelations in both H and V channels, as well as the cross-correlation. The detection obtained in this manner is a nonlinear function of the signal parameters, thus making the evaluation of the threshold that maintains an acceptable false alarm rate, quite cumbersome. In this paper, we investigate an improved version of this approach wherein each term in the sum is weighted appropriately to maximize the rate of detection for a given false alarm rate.

Available online at http://erad2008.fmi.fi/proceedings/extended/erad2008-0008-extended.pdf.

Ivic, I., S. Torres, 2009: Using signal coherency to improve detection on weather radars. Extended Abstracts, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P5.8.

Ivic, I. R., D. S. Zrnic, T. Yu, 2009: The Use of Coherency to Improve Signal Detection in Dual-Polarization Weather Radars. Journal of Atmospheric and Oceanic Technology, 26, 2474-2487.

Currently, signal detection and censoring in operational weather radars is performed using thresholds of estimated signal-to-noise ratio (SNR) and/or magnitude of autocorrelation coefficient at the first temporal lag. Growing popularity of polarimetric radars prompts the quest for improved detection schemes that take advantage of the signals from the two orthogonally polarized electric fields. A hybrid approach is developed based on the sum of the cross-correlation estimates as well as the powers and autocorrelations from each of the dual-polarization returns. The hypothesis that “signal is present” is accepted if the sum exceeds a predetermined threshold. Otherwise, data are considered to represent noise and are censored. The threshold is determined by the acceptable rate of false detections that is less than or equal to a preset value. The scheme is evaluated both in simulations and through implementation on time-series data collected by the research weather surveillance radar (KOUN) in Norman, Oklahoma.

Available online at http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F2009JTECHA1154.1.

Ivic, I. R., 2009: Detection Thresholds for Spectral Moments and Polarimetric Variables. VDM Verlag Dr. Muller, 199 pp.

The most significant advancement in weather radars over the last two decades is polarization diversity, so much so, that the US National Weather Service is introducing this capability to its national network of Doppler radars. Introduction of dual-polarization brings new information that can be used for separating signals from noise. Classical approaches apply thresholds on estimated signal-to-noise ratio (SNR) and/or the magnitude of autocorrelation coefficient at lag one. Because the weather signals from the two orthogonally polarized electric fields are highly correlated this feature can be used to enhance the detection. This book provides a comprehensive analysis of a novel approach that combines estimates of powers, autocorrelations, and cross-correlation to effectively enhance the signal detection on the polarimetric weather radars. The book gives detailed description of a computationally efficient method suited for real-time implementation. Principles and approaches laid out are general and can be applied to other cases where sensing of partially coherent signals is of interest. Moreover methods for evaluating probabilities at the tails of density functions are exposed.

Ivic, I., S. Torres, 2010: Online estimation of noise power for weather radars. Preprints, 6th European Conf. on Radar in Meteorology and Hydrology: Adv. in Radar Technology, Sibiu, Romania, National Meteorological Administration, Romania, 30-36.

Ivic, I. R., S. M. Torres, 2011: Online Estimation of Noise Power for Weather Radars. Extended Abstracts, 27th Conference on Interactive Information and Processing Systems (IIPS), Seattle, WA, USA, NSSL/CIMMS, 369.

Radar antenna intercepts thermal radiation from various sources including ground, precipitation, sun, sky, or man-made radiators. Consequently, depending on where the antenna is pointing, the receiver noise power will vary routinely. This creates possibility for incorrect noise power measurements which may lead to reduction of coverage in cases where noise power is overestimated or to radar data images cluttered by noise speckles if the noise power is underestimated. Moreover, when an erroneous noise power is used at low signal-to-noise ratios, estimators usually produce biased meteorological variables such as in the case of reflectivity and spectrum width. Therefore, to obtain the best quality of radar products it is desirable to estimate receiver noise for each radial and account for it in the computation of the radar variables. Currently, most weather radars estimate system noise power by either offline measurements or through periodic automatic calibrations as in the NEXRAD network.
Ideally, noise power estimates should be computed for every sampling volume, for example, by using spectral noise estimation methods. However, techniques such as those proposed by Hildebrand and Sekhon (1974), and Urkowitz and Nespor (1992, 1994) introduce significant bias in noise power estimates for radar volumes with weather
signals that have wide spectrum or if using a small number of samples. Hence, a need arises for a more precise and continuous system noise power calibration
that is robust and feasible for real-time implementation on weather radars.
In this paper, we propose an effective method to estimate the system noise power dynamically from the in-phase and quadrature data for every antenna position (radial). The technique uses a novel criterion to detect radar volumes that do not contain significant weather signals from which to estimate the system noise power. This technique is evaluated using time-series data collected with the National Weather Radar Testbed Phased-Array Radar (NWRT) and the research WSR-88D KOUN radar, both located in Norman, OK. Results show that the proposed technique produces noise power estimates that are closely matched to the ones obtained from manually identified, signal-free radar volumes at far ranges from the radar; thus, providing empirical validation. A real-time implementation of this technique is expected to significantly improve the data quality of operational weather radars which often rely on accurate noise power estimates.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper180709.html.

Ivic, I. R., V. Melnikov, 2011: Enhancing signal detection in dual-polarization weather radars by combining the coherency based detection and 2D despeckling. Extended Abstracts, 35-th Conference on Radar Meteorology, Pittsburgh, PA, USA, AMS, 191126.

Mitigation of 3-dB losses in dual-pol WSR-88Ds.

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper191126.html.

James, M. R., R. D. Palmer, T.-Y. Yu, S. M. Torres, R. J. Doviak, D. S. Zrnic, 2005: Implementation of refractivity retrieval from ground clutter using the S-band KOUN radar. Preprints, 32nd International Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, 4R.7.

Jorgensen, D. P., M. N. Hanshaw, K. M. Schmidt, J. L. Laber, D. M. Staley, J. W. Kean, P. J. Restrepo, 2011: Value of a Dual-Polarized Gap-Filling Radar in Support of Southern California Post-Fire Debris-Flow Warnings. J. Hydrometeor., 12, 1581-1595.

A portable truck-mounted C-band Doppler weather radar was deployed to observe rainfall over the Station Fire burn area near Los Angeles, California, during the winter of 2009/10 to assist with debris-flow warning decisions. The deployments were a component of a joint NOAA–U.S. Geological Survey (USGS) research effort to improve definition of the rainfall conditions that trigger debris flows from steep topography within recent wildfire burn areas. A procedure was implemented to blend various dual-polarized estimators of precipitation (for radar observations taken below the freezing level) using threshold values for differential reflectivity and specific differential phase shift that improves the accuracy of the rainfall estimates over a specific burn area sited with terrestrial tipping-bucket rain gauges. The portable radar outperformed local Weather Surveillance Radar-1988 Doppler (WSR-88D) National Weather Service network radars in detecting rainfall capable of initiating post-fire runoff-generated debris flows. The network radars under- estimated hourly precipitation totals by about 50%. Consistent with intensity–duration threshold curves determined from past debris-flow events in burned areas in Southern California, the portable radar-derived rainfall rates exceeded the empirical thresholds over a wider range of storm durations with a higher spatial resolution than local National Weather Service operational radars. Moreover, the truck-mounted C-band radar dual-polarimetric-derived estimates of rainfall intensity provided a better guide to the expected severity of debris-flow events, based on criteria derived from previous events using rain gauge data, than traditional radar-derived rainfall approaches using reflectivity–rainfall relationships for either the portable or opera- tional network WSR-88D radars. Part of the reason for the improvement was due to siting the radar closer to the burn zone than the WSR-88Ds, but use of the dual-polarimetric variables improved the rainfall estimation by ~12% over the use of traditional Z–R relationships.

Kain, J. S., S. J. Weiss, J. J. Levit, M. E. Baldwin, D. R. Bright, 2006: Examination of convection-allowing configurations of the WRF model for the prediction of severe convective weather: The SPC/NSSL Spring Program 2004. Weather and Forecasting, 21, 167-181.

Convection-allowing configurations of the Weather Research and Forecast (WRF) model were evaluated during the 2004 Storm Prediction Center–National Severe Storms Laboratory Spring Program in a simulated severe weather forecasting environment. The utility of the WRF forecasts was assessed in two different ways. First, WRF output was used in the preparation of daily experimental human forecasts for severe weather. These forecasts were compared with corresponding predictions made without access to WRF data to provide a measure of the impact of the experimental data on the human decision-making process. Second, WRF output was compared directly with output from current operational forecast models. Results indicate that human forecasts showed a small, but measurable, improvement when forecasters had access to the high-resolution WRF output and, in the mean, the WRF output received higher ratings than the operational Eta Model on subjective performance measures related to convective initiation, evolution, and mode. The results suggest that convection-allowing models have the potential to provide a value-added benefit to the traditional guidance package used by severe weather forecasters.

Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, J. J. Levit, G. W. Carbin, C. S. Schwartz, M. L. Weisman, K. K. Droegemeier, D. B. Weber, K. W. Thomas, 2007: Some practical considerations for the first generation of operational convection-allowing NWP: How much resolution is enough?. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.5.

Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, J. J. Levit, G. W. Carbin, C. S. Schwartz, M. L. Weisman, K. K. Droegemeier, D. B. Weber, K. W. Thomas, 2008: Some practical considerations regarding horizontal resolution in the first generation of operational convection-allowing NWP. Weather and Forecasting, 23, 931-952.

During the 2005 NOAA Hazardous Weather Testbed Spring Experiment two different highresolution
configurations of the WRF-ARW model were used to produce 30 h forecasts five days
a week for a total of 7 weeks. These configurations used the same physical parameterizations and
the same input dataset for initial and boundary conditions, differing primarily in their spatial resolution.
The first set of runs used 4 km horizontal grid spacing with 35 vertical levels while the
second used 2 km grid spacing and 51 vertical levels.
Output from these daily forecasts is analyzed to assess the numerical forecast sensitivity to
spatial resolution in the upper end of the convection-allowing range of grid-spacing. The analysis
is based on a combination of visual comparison, systematic subjective verification conducted during
the Spring Experiment, and objective metrics based largely on the mean diurnal cycle of simulated
reflectivity and precipitation fields. Additional insight is gained by examining the size
distributions of individual reflectivity and precipitation entities and by comparing forecasts of
mesoscyclone characteristics in the two sets of forecasts.
In general, the 2 km forecasts provide more detailed presentations of convective activity, but
there appears to be little, if any, forecast skill on the scales where the added details emerge. On
the scales where both model configurations show higher levels of skill - the scale of mesoscale
convective features - the forecasts appear to provide comparable utility for severe weather forecasters.
These results suggest that 4 km grid spacing is a good place to start for the first generation
of 1-2 day convection-permitting operational NWP.

Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, J. J. Levit, G. W. Carbin, C. S. Schwartz, M. L. Weisman, K. K. Droegemeier, 2007: Some practical considerations for the first generation of operational convection-allowing NWP: How much resolution is enough?. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.5. [Available from John S. Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

During the 2005 NOAA Hazardous Weather Testbed Spring Experiment (formerly known as the SPC/NSSL Spring Program) two different high-resolution configurations of the WRF-ARW model were used to produce 30 h forecasts five days a week for a total of 7 weeks. These configurations used the same physical parameterizations and the same input dataset for initial and boundary conditions, differing primarily in their spatial resolution. The first set of runs used 4 km horizontal grid spacing with 35 vertical levels while the second used 2 km grid spacing and 51 vertical levels.

This setup provided an unprecedented opportunity to assess the sensitivity to spatial resolution in the upper end of the convection-allowing range of grid-spacing, during many different severe-weather events. Of particular interest was whether the ~ ten fold increase in computing expense required by the 2 km runs could be justified by added value in the higher resolution forecasts. In this study, we examine and compare these forecasts from several different perspectives. First, we provide a visual examination of simulated reflectivity fields from selected convective events, highlighting the differences that might be detected by an operational forecaster – differences between the two model runs and the ways that both differ from observed reflectivity fields. Next, we present the results of subjective assessments of forecast skill, based on daily ratings assigned by panels of experts during the Spring Experiment. Then, we move on to objective measures of skill. These measures are based on time-averaged behavior characteristics of the models rather than selected points in time and space. For example, we examine the mean diurnal trends of simulated reflectivity and accumulated precipitation fields, as compared with observations. We compare the size distributions of individual reflectivity and precipitation entities, or “storms”, and we look at measures of storm rotation. Further, we look at traditional verification statistics such as equitable-threat and bias scores.

In general, we find that meteorological fields from the two model configurations behave much more like each other than like observations. The 2 km forecasts provide more detailed structures and appear to provide more realistic depictions of supercell-like storm configurations, both of which are intriguing to severe weather forecasters, but neither configuration shows much skill in predicting these small-scale features. On the scales where they show higher levels of skill – the scale of mesoscale convective features – the forecasts are often quite similar. The implications of these results, i.e., the value added by doubling resolution in this context, will be discussed at the conference.

Available online at http://ams.confex.com/ams/pdfpapers/124513.pdf.

Kain, J. S., S. J. Weiss, S. R. Dembek, J. J. Levit, D. R. Bright, J. L. Case, M. C. Coniglio, A. R. Dean, R. Sobash, 2008: Severe-weather forecast guidance from the first generation of large domain convection-allowing models: Challenges and opportunities. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor Soc., CD-ROM, 12.1. [Available from John Kain, NSSL, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Kain, J. S., M. Xue, M. C. Coniglio, S. J. Weiss, F. Kong, T. L. Jensen, B. G. Brown, J. Gao, K. Brewster, K. W. Thomas, Y. Wang, C. S. Schwartz, J. J. Levit, 2010: Assessing advances in the assimilation of radar data within a collaborative forecasting-research environment. Weather and Forecasting, 25, 1510-1521.

The impacts of assimilating radar data and other mesoscale observations in real-time, convection-allowing model forecasts were evaluated during the spring seasons of 2008 and 2009 as part of the Hazardous Weather Test Bed Spring Experiment activities. In tests of a prototype continental U.S.-scale forecast system, focusing primarily on regions with active deep convection at the initial time, assimilation of these observations had a positive impact. Daily interrogation of output by teams of modelers, forecasters, and verification experts provided additional insights into the value-added characteristics of the unique assimilation forecasts. This evaluation revealed that the positive effects of the assimilation were greatest during the first 3–6 h of each forecast, appeared to be most pronounced with larger convective systems, and may have been related to a phase lag that sometimes developed when the convective-scale information was not assimilated. These preliminary results are currently being evaluated further using advanced objective verification techniques.

Kain, J. S., S. R. Dembek, S. J. Weiss, J. L. Case, J. J. Levit, R. A. Sobash, 2010: Extracting unique information from high resolution forecast models: Monitoring selected fields and phenomena every time step. Weather and Forecasting, 25, 1536-1542.

A new strategy for generating and presenting model diagnostic fields from convection-allowing forecast models is introduced. The fields are produced by computing temporal-maximum values for selected diagnostics at each horizontal grid point between scheduled output times. The two-dimensional arrays containing these maximum values are saved at the scheduled output times. The additional fields have minimal impacts on the size of the output files and the computation of most diagnostic quantities can be done very efficiently during integration of the Weather Research and Forecasting Model. Results show that these unique output fields facilitate the examination of features associated with convective storms, which can change dramatically within typical output intervals of 1–3 h.

Kang, M., S. E. Giangrande, A. V. Ryzhkov, D. Lee, 2005: Polarimetric Rainfall Measurements in Localized Strong Convection. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P9R.12.

Kanofsky, L. M., P. B. Chilson, T. J. Schuur, G. Zhang, E. Brandes, 2005: A comparative study of drop size distribution retrieval using two video disdrometers and a UHF wind profiling radar. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P14R.3.

Kanofsky, L. M., P. B. Chilson, T. J. Schuur, G. Zhang, Q. Cao, E. Brandes, 2007: Quantitative precipitation estimation and error analysis with a UHF wind profiling radar and a two-dimensional video disdrometer. Preprints, 33rd Conference on radar Meteorology, Cairns, Australia, American Meteorological Society, P13B.6.

Kaplan, M., C. Adaniya, P. Marzette, K. King, S. Underwood, J. Lewis, 2009: The role of upstream mid-tropospheric circulations in Sierra Nevada leeside (spillover precipitation): Part II: Secondary atmospheric river accompanying a mid-level jet. J. Hydrometeor., 10, 1327-1354.

Kaplan, M. L., R. K. Vellore, J. M. Lewis, M. Young, 2011: The role of unbalanced mesoscale circulations in dust storms. Journal of Geophysical Research - D: Atmospheres, 116, 218-247.

In this study, two dust storms in northwestern Nevada (February 2002 and April 2004) are investigated through the use of Weather Research and Forecasting (WRF) model simulations. The focus of the study is twofold: (1) Examination of dynamic processes on the meso‐b scale for both cases, and (2) analysis of extreme upper‐air cooling prior to storm formation and the development of a nearly discontinuous gust front in the 2002 case that could not be validated in an earlier synoptic‐scale study. Results of the simulations suggest that the driving mechanism for dust storm dynamics derives from the breakdown and subsequent balance between the advection of geostrophic wind and total wind in the exit region of the polar jet. In this process, the deviation from quasi‐geostrophic (Q‐G) balance creates a plume of ascent along and to the right of the jet’s exit region. The cold pool generation in the mid‐lower troposphere in consequence of this adjustment sets up the kinetic energy in the planetary boundary layer and creates a forward leaning (slope from north to south) cold front under the jet exit region. Surface heating is coupled with this frontal structure, and rapid surface pressure falls (rises) occur initially (later) in response to diabatic (adiabatic) processes. The adjustments occur at fast time scales, scales that are radically different from those in studies that followed the Q‐G tenets of the Danielsen paradigm. The results of this study indicate that meso‐b scale features associated with subgeostrophy in the exit region of the curved jet aloft and associated thermal wind imbalance (700–500 hPa) lead to significant velocity divergence aloft. Mass/momentum adjustments and the associated cooling strengthen the baroclinic zone aloft. The restoration to thermal wind balance accompanying this cooling resulted in a narrow zone of surface pressure rise and strong low‐level isallobaric winds. The turbulent momentum for dust ablation comes

Katz, S., D. Lafrance, H. Urkowitz, D. Staiman, M. Campbell, D. Forsyth, 2006: Solid State Fractional Phased Array Addition To NWRT. Extended Abstracts, 22nd International Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, 11.7.

The National Weather Radar Testbed (NWRT) serves as a tool for radar meteorological research and for investigation of techniques for utilizing phased array radars for weather sensing. Using a SPY-1A phased array antenna, loaned to NOAA by the U. S. Navy, the testbed is capable of performing scans over user-defined sectors considerably faster than conventional weather radars using rotating reflector antennas. Lockheed Martin and NSSL are planning an addition to the NWRT in the form of a solid state transmit/receive (T/R) module fractional array. This array will provide a proof of concept capability for advanced phased array applications to meteorological sensing and multifunction applications. In particular, implementation will support validation of concepts such as dual polarization control and calibration over all scan angles, digital beamforming, beam multiplexing, site specific nulling of point clutter, split array processing for wind direction estimation and real time dwell scheduling to support adaptive scan algorithms. In this paper we provide an overview of the proposed fractional array capabilities, integration with NWRT and some of the radar design tradeoffs that may be required as the project proceeds

Kelleher, K. E., K. K. Droegemeier, J. J. Levit, C. S. Sinclair, D. E. Jahn, S. D. Hill, L. Mueller, G. Qualley, T. D. Crum, S. D. Smith, S. A. Del Greco, S. Lakshmivarahan, L. Miller, M. Ramamurthy, B. Domenico, D. W. Fulker, 2007: Project CRAFT: A Real-Time Delivery System for NEXRAD Level II Data Via the Internet. Bulletin of the American Meteorological Society, 88, 1045-1057.

The NOAA NWS announced at the annual meeting of the American Meteorological Society in February 2003 its intent to create an Internet-based pseudo-operational system for delivering Weather Surveillance Radar-1988 Doppler (WSR-88D) Level II data. In April 2004, the NWS deployed the Next-Generation Weather Radar (NEXRAD) level II central collection functionality and set up a framework for distributing these data. The NWS action was the direct result of a successful joint government, university, and private sector development and test effort called the Collaborative Radar Acquisition Field Test (CRAFT) project. Project CRAFT was a multi-institutional effort among the Center for Analysis and Prediction of Storms, the University Corporation for Atmospheric Research, the University of Washington, and the three NOAA organizations, National Severe Storms Laboratory, WSR-88D Radar Operations Center (ROC), and National Climatic Data Center. The principal goal of CRAFT was to demonstrate the real-time compression and Internet-based transmission of level II data from all WSR-88D with the vision of an affordable nationwide operational implementation. The initial test bed of six radars located in and around Oklahoma grew to include 64 WSR-88D nationwide before being adopted by the NWS for national implementation. A description of the technical aspects of the award-winning Project CRAFT is given, including data transmission, reliability, latency, compression, archival, data mining, and newly developed visualization and retrieval tools. In addition, challenges encountered in transferring this research project into operations are discussed, along with examples of uses of the data.

Khain, A., A. Ryzhkov, M. Pinsky, A. Pokrovsky, 2008: Simulation of polarimetric radar parameters using a cloud model with spectral bin microphysics. Extended Abstracts, 5th Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Vaisala, CD-ROM, P7.7.

Khain, A., A. Pokrovsky, D. Rosenfeld, U. Blahak, A. Ryzhkov, 2011: Effects of aerosols on precipitation and hail production in a midlatitude storm as seen from simulations using spectral (bin) microphysics model. Atmospheric Research, 99, 129-146.

Khan, S. I., Y. Hong, J. Wang, K. K. Yilmaz, J. J. Gourley, R. F. Adler, G. R. Brakenridge, F. Policelli, S. Habib, D. Irwin, 2011: Satellite remote sensing and hydrological modeling for flood inundation mapping in Lake Victoria Basin: Implications for hydrologic prediction in ungauged basins. IEEE Transactions on Geoscience and Remote Sensing, 49, 85-95.

Kitzmiller, D. H., F. Ding, S. Van Cooten, K. Howard, C. Langston, J. Zhang, H. Moser, R. J. Kuligowski, D. Kim, Y. Zhang, D. Riley, 2008: A comparison of evolving multisensor precipitation estimation methods based on impacts on flow prediction using a distributed hydrologic model. Extended Abstracts, 22nd Conference on Hydrology, Poster Session 3 Validation of Hydrometeorological Observations, New Orleans, LA, USA, AMS, CD-ROM, P3.4.

Evolving methodologies for multisensor precipitation estimation are being investigated to determine their influence on the flow predictions of a distributed hydrologic model. These methods include the National Mosaic and Quantitative Precipitation algorithm package (NMQ) under development at the National Severe Storms Laboratory, the Multisensor Precipitation Estimator package (MPE) currently operational at National Weather Service field offices, and the Self-Calibrating Multivariate Precipitation Retrieval algorithm (SCaMPR) under development within the National Environmental Satellite, Data, and Information Service Center for Satellite Applications and Research. Our goal is to determine which combination of algorithm features offer the greatest benefit toward operational hydrologic forecasting. These features include automated radar quality control, range correction, and methods of multiple-radar data compositing, all of which vary among NMQ, MPE, and SCaMPR.

All methods described above have been applied to deriving high-resolution (4-km hourly) gridded precipitation estimates over and near the Tar River Basin of North Carolina through the course of several precipitation events during the period December 2004-January 2005. The NMQ and MPE algorithms are driven by identical WSR-88D reflectivity and rain gauge input. The GOES infrared-based SCaMPR algorithm is calibrated by comparison with contemporaneous radar rainrate fields from the NMQ. All results are currently being compared to an independent set of hourly and daily rain gauge reports; the various precipitation grids will later be input to the NWS Hydrology Laboratory - Research Distributed Hydrologic Model, to determine impacts on the quality of its discharge simulations at several gauged points on the Tar River and its tributaries. Further results will be reported in our extended abstract.

Available online at http://ams.confex.com/ams/88Annual/techprogram/paper_134451.htm.

Kitzmiller, D. H., F. Ding, S. Van Cooten, K. Howard, C. Langston, J. Zhang, H. Moser, R. J. Kuligowski, D. Kim, Y. Zhang, D. Riley, 2008: A comparison of evolving multisensor precipitation estimation methods based on impacts on flow prediction using a distributed hydrologic model. Extended Abstracts, 22nd Conference on Hydrology, Poster Session 3 Validation of Hydrometeorological Observations, New Orleans, LA, USA, AMS, CD-ROM, P3.4.

Evolving methodologies for multisensor precipitation estimation are being investigated to determine their influence on the flow predictions of a distributed hydrologic model. These methods include the National Mosaic and Quantitative Precipitation algorithm package (NMQ) under development at the National Severe Storms Laboratory, the Multisensor Precipitation Estimator package (MPE) currently operational at National Weather Service field offices, and the Self-Calibrating Multivariate Precipitation Retrieval algorithm (SCaMPR) under development within the National Environmental Satellite, Data, and Information Service Center for Satellite Applications and Research. Our goal is to determine which combination of algorithm features offer the greatest benefit toward operational hydrologic forecasting. These features include automated radar quality control, range correction, and methods of multiple-radar data compositing, all of which vary among NMQ, MPE, and SCaMPR.

All methods described above have been applied to deriving high-resolution (4-km hourly) gridded precipitation estimates over and near the Tar River Basin of North Carolina through the course of several precipitation events during the period December 2004-January 2005. The NMQ and MPE algorithms are driven by identical WSR-88D reflectivity and rain gauge input. The GOES infrared-based SCaMPR algorithm is calibrated by comparison with contemporaneous radar rainrate fields from the NMQ. All results are currently being compared to an independent set of hourly and daily rain gauge reports; the various precipitation grids will later be input to the NWS Hydrology Laboratory - Research Distributed Hydrologic Model, to determine impacts on the quality of its discharge simulations at several gauged points on the Tar River and its tributaries. Further results will be reported in our extended abstract.

Available online at http://ams.confex.com/ams/88Annual/techprogram/paper_134451.htm.

Kitzmiller, D., S. Van Cooten, F. Ding, K. Howard, C. Langston, J. Zhang, H. Moser, Y. Zhang, J. Gourley, D. Kim, D. Riley, 2011: Evolving multisensor precipitation estimation methods: Their impacts on flow prediction using a distributed hydrologic model. Journal of Hydrometeorology, 12, 1414-1431.

This study investigates evolving methodologies for radar and merged gauge–radar quantitative precipitation estimation (QPE) to determine their influence on the flow predictions of a distributed hydrologic model. These methods include the National Mosaic and QPE algorithm package (NMQ), under development at the National Severe Storms Laboratory (NSSL), and the Multisensor Precipitation Estimator (MPE) and High-Resolution Precipitation Estimator (HPE) suites currently operational at National Weather Service (NWS) field offices. The goal of the study is to determine which combination of algorithm features offers the greatest benefit toward operational hydrologic forecasting. These features include automated radar quality control, automated Z–R selection, brightband identification, bias correction, multiple radar data compositing, and gauge–radar merging, which all differ between NMQ and MPE–HPE. To examine the spatial and temporal characteristics of the precipitation fields produced by each of the QPE methodologies, high-resolution (4 km and hourly) gridded precipitation estimates were derived by each algorithm suite for three major precipitation events between 2003 and 2006 over subcatchments within the Tar–Pamlico River basin of North Carolina. The results indicate that the NMQ radar-only algorithm suite consistently yielded closer agreement with reference rain gauge reports than the corresponding HPE radar-only estimates did. Similarly, the NMQ radar-only QPE input generally yielded hydrologic simulations that were closer to observations at multiple stream gauging points. These findings indicate that the combination of Z–R selection and freezing-level identification algorithms within NMQ, but not incorporated within MPE and HPE, would have an appreciable positive impact on hydrologic simulations. There were relatively small differences between NMQ and HPE gauge–radar estimates in terms of accuracy and impacts on hydrologic simulations, most likely due to the large influence of the input rain gauge information.

Kolodziej, A. G., V. Lakshmanan, T. M. Smith, 2011: The development of a storm type climatology using an automated storm classification system. Extended Abstracts, 27th Conference on Interactive Information Processing Systems (IIPS), Seattle, WA, USA, AMS, 9.

This study investigates the use of a storm classification algorithm to produce a preliminary climatology of storm types throughout the United States. Automatic algorithms could conceivably use probabilities derived from environmental data, radar data, and storm type to nowcast hazards associated with storms. Such products could enhance efficiency of real-time forecasting operations during a busy shift with minimal staffing, such as during a tornado outbreak, when the forecaster cannot supervise all significant attributes of a growing storm.

The automated approach to classifying convective storms is based upon both environmental and radar data by means of a K-Means clustering and watershed segmentation algorithm. Radar and environmental data, which were extracted from the generated clusters, provided the data for the development and training of decision tree models to predict storm types. These decision trees generated a preliminary climatology of storm types for the CONUS. Both seasonal and regional characteristics were investigated for dates between February 2009 through December 2009.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper180517.html.

Kong, F., M. Xue, K. W. Thomas, Y. Wang, J. S. Kain, S. J. Weiss, D. R. Bright, J. Du, K. K. Droegemeier, 2008: Real-Time Storm-Scale Ensemble Forecast 2008 Spring Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 12.3. [Available from Fanyou Kong, CAPS, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_141827.htm.

Kong, F., M. Xue, K. W. Thomas, Y. Wang, K. A. Brewster, J. Gao, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. C. Coniglio, J. Du, 2009: A real-time storm-scale ensemble forecast system: 2009 Spring Experiment. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Omaha, NE, USA, Amer. Meteor. Soc., CD-ROM, 16A.3. [Available from Fanyou Kong, CAPS, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/23WAF19NWP/techprogram/paper_154118.htm.

Koracin, D., J. Businger, C. Dorman, J. Lewis, 2005: Formation, evolution, and dissipation of coastal sea fog. Bound.-Layer Meteorol., 117, 447-478.

Koracin, D., D. Leipper, J. Lewis, 2005: Modeling sea fog on the U. S. California coast during a hot spell event. Geofizika, 22, 59-82.

Koracin, D., J. Businger, C. Dorman, J. Lewis, 2005: Formation, evolution, and dissipation of coastal sea fog. Bound. - Layer Meteorol., 117, 447-478.

Koracin, D., D. Liepper, J. Lewis, 2005: Modeling sea fog on the U. S. California coast during a hot spell event. Geofizika, 22, 59-82.

Kuhlman, K. M., C. L. Ziegler, E. R. Mansell, D. R. MacGorman, J. M. Straka, 2006: Numerically Simulated Electrification and Lightning of the 29 June 2000 STEPS Supercell Storm. Monthly Weather Review, 134, 2734-2757.

A three-dimensional dynamic cloud model incorporating airflow dynamics, microphysics, and thunderstorm electrification mechanisms is used to simulate the first 3 h of the 29 June 2000 supercell from the Severe Thunderstorm Electrification and Precipitation Study (STEPS). The 29 June storm produced large flash rates, predominately positive cloud-to-ground lightning, large hail, and an F1 tornado. Four different simulations of the storm are made, each one using a different noninductive (NI) charging parameterization. The charge structure, and thus lightning polarity, of the simulated storm is sensitive to the treatment of cloud water dependence in the different NI charging schemes. The results from the simulations are compared with observations from STEPS, including balloon-borne electric field meter soundings and flash locations from the Lightning Mapping Array. For two of the parameterizations, the observed “inverted” tripolar charge structure is well approximated by the model. The polarity of the ground flashes is opposite that of the lowest charge region of the inverted tripole in both the observed storm and the simulations. Total flash rate is well correlated with graupel volume, updraft volume, and updraft mass flux. However, there is little correlation between total flash rate and maximum updraft speed. Based on the correlations found in both the observed and simulated storm, the total flash rate appears to be most representative of overall storm intensity.

Available online at http://www.ametsoc.org.

Kuhlman, K., D. MacGorman, M. Biggerstaff, W. D. Rust, T. Schuur, C. Ziegler, P. Krehbiel, 2006: Lightning and radar observatons of the 29 May 2004 supercell during TELEX. Preprints, 2nd Conference on Meteorological Applications of Lightning Data, Atlanta, GA, USA, American Meteorological Society, 3.3.

Kuhlman, K. M., E. R. Mansell, C. L. Ziegler, M. I. Biggerstaff, D. R. MacGorman, D. C. Dowell, 2008: EnKF data assimilation and dual-Doppler analysis of the 29 May 2004 Geary, Oklahoma supercell. Proc. 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, P5.1.

On 29 May 2004, a long-track supercell storm moved across Oklahoma producing multiple tornadoes and numerous reports of large hail. Two mobile, C-band, Doppler (SMART-R) radars collected data in 2.5 min volume scans almost continuously for more than three hours. Dual-Doppler analyses were completed for select times using a1 km grid spacing and a 2-pass Barnes objective analysis in the interpolation of radial velocities and reflectivity to a Cartesian grid following Majcen et al (2008).

The focus of the radar data assimilation for this study is to retrieve the state of the storm rather than to develop forecast applications. For this purpose, the ensemble Kalman filter (EnKF) technique is used to assimilate reflectivity and/or radial velocity data into the model from SMART radar at approximately five minute intervals. Comparisons of the simulations employing EnKF to a simulation without data assimilation and to the dual-Doppler syntheses at various times of the storm's life-cycle will be presented. These results will be used to quantify the agreement between the simulation and the observations providing background such that future studies may use the simulations in order to to retrieve unobserved fields.

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142031.htm.

Kuhlman, K. M., D. R. MacGorman, E. R. Mansell, C. L. Ziegler, M. I. Biggerstaff, 2010: A SIMULATION OF ELECTRIFICATION AND LIGHTNING IN A SUPERCELL STORM USING ENKF TO ASSIMILATE DOPPLER RADAR OBSERVATIONS. Proc. International Lightning Meteorology Conferance, Orlando, FL, USA, Vaisala, 1-8.

Available online at http://www.vaisala.com/Vaisala%20Documents/Scientific%20papers/14.Kuhlman,%20MacGorman,%20Mansell.pdf.

Kuhlman, K. M., E. R. Mansell, D. R. MacGorman, C. L. Ziegler, M. I. Biggerstaff, 2010: Electrification and Lightning in Simulations of the 29 May 2004 Geary, OK Storm Using EnKF Data Assimilation. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, American Meteorological Society, 13A.7.

On 29 May 2004, a line of convective cells formed along a dryline near Elk City, OK; one intensified to a heavy-precipitation (HP) supercell north of Weatherford, OK as it moved into the TELEX domain (MacGorman et al. 2008). The data set established through this field campaign provides an excellent opportunity for using Ensemble Kalman Filter (EnKF) assimilation of radar data to produce a storm simulation having characteristics similar to those of the observed storm, so that we can examine hypotheses concerning the storm's electrification and lightning.

The Collaborative Model for Multiscale Atmospheric Simulation (COMMAS) was used to produce the simulations. Radial velocity and reflectivity data from a single mobile doppler radar were assimilated into the the COMMAS model using two-moment microphysics, including seven hydrometeor categories, and parameterizations for electrification and lightning with a horizontally homogeneous base state. The simulated precipitation and wind fields were similar to those of the observed storm. Simulated lightning flash rates were very large, as was observed, and the distribution of charge in the main body of the storm revealed in the simulation details the lightning dependence on storm kinematics that could not be directly observed. The simulation produced the observed lightning holes and the high-altitude lightning seen in the observations. However, the simulation failed to produce the observed lightning initiations (or even lightning channels) in the distant downstream anvil; instead, the simulated lightning was confined to the main body of the storm.

Kumjian, M. R., A. V. Ryzhkov, 2007: Polarimetric characteristics of tornadic and nontornadic supercell storms. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P10.1.

Kumjian, M. R., A. V. Ryzhkov, J. L. Alford, M. Knight, J. W. Conway, 2008: Close-range observations of a tornadic supercell with C-band polarimetric Doppler radar. Extended Abstracts, Symposium on Recent Developments in Atmospheric Applications of Radar and Lidar, 88th Annual Meeting, New Orleans, LA, USA, American Meteorological Society, P2.14.

Kumjian, M. R., A. V. Ryzhkov, 2008: Microphysical size sorting revealed by dual-polarization Doppler radar. Extended Abstracts, Symposium on Recent Developments in Atmospheric Applications of Radar and Lidar, 88th Annual Meeting, New Orleans, LA, USA, American Meteorological Society, P2.13.

Kumjian, M. R., A. V. Ryzhkov, 2008: Polarimetric signatures in supercell thunderstorms. Journal of Applied Meteorology and Climatology, 47, 1940-1961.

Kumjian, M. R., A. V. Ryzhkov, 2008: Interpretation of polarimetric signatures in supercell storms using explicit microphysical modeling. Extended Abstracts, 5th European Radar Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Finnish Meteorological Institute, CD-ROM, P7.2.

Available online at http://erad2008.fmi.fi/proceedings/extended/erad2008-0065-extended.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2008: Microphysical analysis of supercell rear-flank downdrafts using dual-polarization radar observations. Extended Abstracts, 5th European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Finnish Meteorological Institute, CD-ROM, P7.10.

Available online at http://erad2008.fmi.fi/proceedings/extended/erad2008-0066-extended.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2009: Storm-relative helicity revealed from polarimetric radar measurements. Journal of the Atmospheric Sciences, 66, 667-685.

Kumjian, M. R., J. C. Snyder, A. V. Ryzhkov, D. S. Zrnic, S. Frasier, H. B. Bluestein, 2008: Comparison of polarimetric radar observations of tornadic supercells at S, C, and X bands. Extended Abstracts, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, 5.5.

Available online at http://ams.confex.com/ams/pdfpapers/142020.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2008: Rapid-scan observations of a bow echo storm with a dual-polarization WSR-88D. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, P4.12.

Available online at http://ams.confex.com/ams/pdfpapers/141915.pdf.

Kumjian, M. R., A. V. Ryzhkov, V. Melnikov, 2008: Super-resolution polarimetric observations of a cyclic tornadic supercell. Extended Abstracts, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, P9.13.

Available online at http://ams.confex.com/ams/pdfpapers/141916.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2008: Microphysical differences between tornadic and nontornadic supercell rear-flank downdrafts revealed by dual-polarization radar measurements. Extended Abstracts, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, 3B.4.

Available online at http://ams.confex.com/ams/pdfpapers/141912.pdf.

Kumjian, M., A. Ryzhkov, 2009: The impact of evaporation on polarimetric characteristics of rain. Theoretical model and practical implications. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, P2.11.

Available online at http://ams.confex.com/ams/pdfpapers/155479.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2010: The impact of evaporation on polarimetric characteristics of rain: Theoretical model and practical implications. Journal of Applied Meteorology and Climatology, 49, 1247-1267.

Soon the National Weather Service WSR-88D radar network will be upgraded to allow dual-polarization capabilities. Therefore, it is imperative to understand and identify
microphysical processes using the polarimetric variables. Though melting and size sorting of hydrometeors has been investigated, there has been relatively little focus devoted to the impact of evaporation on the polarimetric characteristics of rainfall. In this study, a simple explicit bin microphysics one-dimensional rainshaft model is constructed to quantify the impact of evaporation (neglecting the collisional processes) on vertical profiles of polarimetric radar variables in rain. Results of this model are applicable for light to moderate rain (< 10 mm hr-1).

The modeling results indicate that the amount of evaporation that occurs in the subcloud layer is strongly dependent on the initial shape of the drop size distribution (DSD) aloft which can be assessed with polarimetric measurements. Understanding how radar-estimated rainfall rates may change in height due to
evaporation is important for quantitative precipitation estimates, especially in regions far from the radar or in regions of complex terrain where low levels may not be adequately sampled. In addition to quantifying the effects of evaporation, we offer a simple method of estimating the
amount of evaporation that occurs in a given environment based on polarimetric radar measurements of reflectivity factor ZH and differential reflectivity ZDR aloft. Such a technique may be useful to operational meteorologists and hydrologists in estimating the amount of precipitation reaching the surface, especially in regions of poor low-level radar coverage such as mountainous regions or locations at large distances from the radar.

Kumjian, M. R., A. V. Ryzhkov, V. Melnikov, T. J. Schuur, 2010: Rapid-scan super-resolution observations of a cyclic supercell with a dual-polarization WSR-88D. Monthly Weather Review, 138, 3762-3786.

In recent years, there has been widespread interest in collecting and analyzing rapid updates of radar data in severe convective storms. To this end, conventional single-polarization rapid-scan radars and phased array radar systems have been employed in numerous studies. However, rapid updates of dual-polarization radar data in storms are not widely available. For this study, a rapid scanning strategy is developed for the polarimetric prototype research Weather Surveillance Radar-1988 Doppler (WSR-88D) radar in Norman, Oklahoma (KOUN), which emulates the future capabilities of a polarimetric multifunction phased array radar (MPAR). With this strategy, data are collected over an 80° sector with 0.5° azimuthal spacing and 250-m radial resolution (“super resolution”), with 12 elevation angles. Thus, full volume scans over a limited area are collected every 71–73 s.

The scanning strategy was employed on a cyclic nontornadic supercell storm in western Oklahoma on 1 June 2008. The evolution of the polarimetric signatures in the supercell is analyzed. The repetitive pattern of evolution of these polarimetric features is found to be directly tied to the cyclic occlusion process of the low-level mesocyclone. The cycle for each of the polarimetric signatures is presented and described in detail, complete with a microphysical interpretation. In doing so, for the first time the bulk microphysical properties of the storm on small time scales (inferred from polarimetric data) are analyzed. The documented evolution of the polarimetric signatures could be used operationally to aid in the detection and determination of various stages of the low-level mesocyclone occlusion.

Kumjian, M. R., S. Ganson, A. V. Ryzhkov, 2010: Polarimetric characteristics of freezing drops: Theoretical model and observations. Proc. 6th European Conference on Radar in Meteorology and Hydrology, Sibiu, Romania, Meteo Romania, 277-282.

Available online at http://www.erad2010.org/pdf/oral/friday/micro/07_ERAD2010_0159.pdf.

Kumjian, M. R., J. C. Picca, S. Ganson, A. V. Ryzhkov, J. Krause, D. S. Zrnic, A. Khain, 2010: Polarimetric radar characteristics of large hail. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, American Meteorological Society, 11.2.

The advantage of dual-polarization radar data in the discrimination of precipitation types has been demonstrated successfully, including the detection of hail among other precipitation echoes. However, the scattering characteristics of hailstones vary widely across the spectrum of sizes and shapes, and are significantly dependent on the degree of melting and the probing radar wavelength. The most substantial societal impact comes from those hailstones considered severe (> 2.5 cm in diameter) by the National Weather Service, as such large hail inflicts the most damage to property. Therefore, it is necessary to determine any distinct polarimetric or scattering properties of such large hail, which will aid in the detection, discrimination, and warning of severe hail events.

This paper explores the polarimetric radar characteristics of large and giant hail using several approaches, including T-Matrix scattering computations, output from bin microphysics models and the Hebrew University Cloud Model, and observations at both S and C bands. The result is a novel set of rules used to discriminate between large (severe) and small hail, taking into account the height of the hailstones relative to the melting layer. The algorithm was tested on several cases including most recent extreme hail event in Oklahoma City on May 16, 2010 for which extensive ground truth is available.

Available online at http://ams.confex.com/ams/pdfpapers/176043.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2010: Precipitation characteristics of supercell hook echoes. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, American Meteorological Society, P8.25.

Recent studies have suggested that thermodynamic properties of supercell rear-flank downdrafts can affect whether or not tornadogenesis occurs. The thermodynamic characteristics of rear-flank downdrafts are determined in part by microphysical processes such as evaporation of raindrops and melting of hailstones. Whereas in situ measurements of changes in the hook echo particle size distributions (PSDs) due to certain microphysical processes are exceedingly rare, polarimetric radars can be used to determine changes in the characteristics of PSDs remotely.

Analysis of polarimetric radar data from numerous supercell hook echoes reveals unusual drop size distributions compared to typical rainfall in Oklahoma, as well as spatially inhomogeneous structures. For example, the inner edge of the hook echo is often characterized by very high ZDR, indicative of a sparse population of very large drops. The bottom and/or back portion of the hook is characterized by moderate to high ZH and rather low ZDR, indicating a surplus of small drops (or lack of larger drops). Hypotheses explaining the unusual drop size distributions are presented.

Available online at http://ams.confex.com/ams/pdfpapers/176042.pdf.

Kumjian, M. R., A. V. Ryzhkov, 2011: Polarimetric radar signatures in supercell storms. Proc. National Radio Science Meeting 2011, Boulder, CO, USA, U.S. National Committee for the International Union of Radio Science, 1096.

Kunkel, K. E., P. Bromirski, H. E. Brooks, T. Cavazos, A. V. Douglas, D. R. Easterling, K. A. Emanuel, P. Y. Groisman, G. J. Holland, T. R. Knutson, J. P. Kossin, P. D. Komar, D. H. Levinson, R. L. Smith, J. Allan, R. Assel, S. Changnon, J. Lawrimore, K. B. Liu, T. Peterson, 2008: Observed Changes in Weather and Climate Extremes. Weather and Climate Extremes in a Changing Climate. Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands. Synthesis and Assessment Product 3.3 Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change, T. M. Karl, G. A. Meehl, C. D. Miller, S. J. Hassol, A. M. Waple, W. L. Murray, Ed(s)., U.S. Climate Change Science Program and the Subcommittee on Glob, 35-80.

LaDue, D., P. Heinselman, cited 2008: Public & Private MeteorologistsGetting to know each other.. [Available online at ://http://www.nwas.org/newsletters/pdf/news_mar2008.pdf.]

LaDue, D. S., P. L. Heinselman, J. F. Newman, 2010: Strengths and limitations of current radar systems for two stakeholder groups in the Southern Plains. Bulletin of the American Meteorological Society, 91, 899-910.

Advancements in radar technology since the deployment of the Weather Surveillance Radar-1988 Doppler (WSR-88D) network have prompted consideration of radar replacement technologies. In order for the outcomes of advanced radar research and development to be the most beneficial to users, an understanding of user needs must be established early in the process and considered throughout. As an important early step in addressing this need, this study explored the strengths and limitations of current radar systems for nine participants from two key stakeholder groups: NOAA's NWS and broadcast meteorologists. Critical incident interviews revealed the role of each stakeholder group and attained stories that exemplified radar strengths and limitations in their respective roles.

NWS forecasters emphasized using radar as an essential tool to assess the current weather situation and communicate hazards to key stakeholder groups. TV broadcasters emphasized adding meaning and value to NWS information and using radar to effectively communicate weather information to viewers. The stories told by our participants vividly illustrated the advancing nature of weather detection with radar, and why there are still issues with weather radar and radar-derived information. Analysis of the stories, which ranged from accounts of severe weather to winter weather, revealed four underlying radar needs: 1) clean, accurate data without intervention, 2) higher spatial- and temporal-resolution data than that provided by the WSR-88D, 3) consistent and low-altitude information, and 4) more accurate information on precipitation type, size, intensity, and distribution.

A supplement to this article is available online:

DOI: 10.1175/2009BAMS2830.2

LaDue, J., C. Spannagle, V. Holtz, S. Torres, K. Elmore, 2010: The impact of WSR-88D Super-Resolution data in low-level mesocyclone evaluation. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, Amer. Meteor. Soc., CD-ROM, P9.8.

In 2008 the resolution of all WSR-88D base products was upgraded, this base data is now routinely used by National Weather Service forecasters in their warning decision making process. We examined the difference in user-defined storm-scale vortex strength at the 0.5 degree elevation between the upgraded resolution and a recombined resolution designed to represent the original “legacy” resolution in 1606 individual volume scans. Each volume scan was determined to be either tornadic or non-tornadic, using a temporal window and Storm Data to establish differences between tornadic and non-tornadic mesocyclones. An analysis of tornado discrimination performance was then created by incrementing a threshold of rotational velocities and performing dichotomous tests depending on whether or not a tornado occurred in association with the mesocyclone within a temporal window surrounding tornado occurrence. We find that a majority of storm-scale vortices, as measured by rotational velocity, are stronger in the upgraded resolution and are also stronger at far distances from the radar. However, the ability of super-resolution velocity data to discriminate tornadic vs. nontornadic mesocyclones shows very small, to almost no difference to that of the recombined velocity data. This later result may be a testimony to the robustness of the recombination algorithm to preserve the strength of mesocyclones.

Lakshmanan, V., G. Stumpf, A. Witt, 2005: A neural network for detecting and diagnosing tornadic circulations using the mesocyclone detection and near storm environment algorithms. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, J5.2.

Lakshmanan, V., G. Stumpf, 2005: A real-time learning technique to predict cloud-to-ground lightning. Preprints, 4th Conference on Artificial Intelligence Applications to Environmental Science, San Diego, CA, USA, American Meteorological Society, CD-ROM, J5.6.

Lakshmanan, V., T. M. Smith, K. Cooper, J. J. Levit, G. J. Stumpf, D. R. Bright, 2006: High-resolution radar data and products over the continental United States. Preprints, 22nd International Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, 9.7.

Lakshmanan, V., I. Adrianto, T. M. Smith, G. J. Stumpf, 2005: A spatiotemporal approach to tornado prediction. Preprints, International Joint Conference on Neural Networks 2005, Montreal, Canada, INNS, 1072.

Lakshmanan, V., T. Smith, K. Hondl, G. Stumpf, A. Witt, 2006: A Real-Time, Three Dimensional, Rapidly Updating, Heterogeneous Radar Merger Technique for Reflectivity, Velocity and Derived Products. Weather and Forecasting, 21, 802-823.

With the advent of real-time streaming data from various radar networks, including most WSR-88Ds and several TDWRs, it is now possible to combine data in real-time to form three-dimensional (3D) multiple-radar grids. We describe a technique for taking the base radar data (reflectivity and radial velocity), and derived products, from multiple radars and combining them in real-time into a rapidly updating 3D merged grid. An estimate of that radar product combined from all the different radars can be extracted from the 3D grid at any time. This is accomplished through a formulation that accounts for the varying radar beam geometry with range, vertical gaps between radar scans, lack of time synchronization between radars, storm movement, varying beam resolutions between different types of radars, beam blockage due to terrain, differing radar calibration and inaccurate time stamps on radar data.

Techniques for merging scalar products like reflectivity as well as innovative, real-time techniques for combining velocity and velocity-derived products are demonstrated. Precomputation techniques that can be utilized to perform the merging in real-time and derived products that can be computed from these three-dimensional merger grids are described.

Available online at http://cimms.ou.edu/~lakshman/Papers/.

Lakshmanan, V., A. Fritz, T. Smith, K. Hondl, G. J. Stumpf, 2007: An automated technique to quality control radar reflectivity data. Journal of Applied Meteorology, 46, 288-305.

Echoes in radar reflectivity data do not always correspond to precipitating particles. Echoes on radar may be due to biological targets such as insects, birds or wind-borne particles, due to anomalous propagation (AP) or ground clutter (GC) or due to test and interference patterns that inadvertently seep into the final products. Although weather forecasters can usually identify, and account for, the presence of such contamination, automated weather radar algorithms are drastically affected.

Several horizontal and vertical features have been proposed to discriminate between precipitation echoes and echoes that do not correspond to precipitation. None of these features by themselves can discriminate between precipitating and non-precipitating areas. In this paper, we use a neural network to combine the individual features, some of which have already been proposed in the literature and some of which we introduce in this paper, into a single discriminator that can distinguish between "good" and "bad" echoes (i.e., precipitation and non-precipitation respectively). The method of computing the horizontal features leads to statistical anomalies in their distributions near the edges of echoes. We describe how to avoid presenting such range gates to the neural network. The gate-by-gate discrimination provided by the neural network is followed by more holistic postprocessing based on spatial contiguity constraints and object identification to yield quality-controlled radar reflectivity scans that have most of the bad echo removed, while leaving most of the good echo untouched. A possible multi-sensor extension, utilizing satellite data and surface observations, to the radar-only technique is also demonstrated. We demonstrate the resulting technique is highly skilled, and that its skill exceeds that of the currently operational algorithm.

Available online at http://cimms.ou.edu/~lakshman/Papers/qcnnjam.pdf.

Lakshmanan, V., K. L. Ortega, T. M. Smith, 2007: Creating spatio-temporal tornado probability forecasts using fuzzy logic and motion variability. Preprints, Fifth Conference on Artificial Intelligence Applications to Environmental Science, San Antonio, TX, USA, AMS, CD-ROM, 2.3.

In this paper, we describe our approach to addressing the problem of creating good probabilistic forecasts when the entity to be forecast can move and morph. We formulate the tornado prediction problem to be one of estimating the probability of an event at a particular spatial location within a given time window. The technique involves clustering Doppler radar-derived fields such as low-level shear and reflectivity to form candidate regions. Assuming stationarity, the spatial probability distribution of this region T minutes ahead is estimated and combined with the probability that the candidate region becomes tornadic T minutes later. Using these two probabilities and the variability of the motion estimates, a spatio-temporal probability field is derived.

The neural network training required to correctly estimate the probabilities has not yet been developed. Therefore, this paper illustrates the underlying idea using fuzzy logic, storm half-life and motion variability.

Available online at http://ams.confex.com/ams/pdfpapers/119456.pdf.

Lakshmanan, V., T. M. Smith, G. J. Stumpf, K. D. Hondl, 2007: The Warning Decision Support System—Integrated Information. Weather and Forecasting, 22, 596-612.

The Warning Decision Support System—Integrated Information (WDSS-II) is the second generation of a system of tools for the analysis, diagnosis, and visualization of remotely sensed weather data. WDSS-II provides a number of automated algorithms that operate on data from multiple radars to provide information with a greater temporal resolution and better spatial coverage than their currently operational counterparts. The individual automated algorithms that have been developed using the WDSS-II infrastructure together yield a forecasting and analysis system providing real-time products useful in severe weather nowcasting. The purposes of the individual algorithms and their relationships to each other are described, as is the method of dissemination of the created products.

Lakshmanan, V., 2007: An overview of radar data compression. Proc. SPIE Optics + Photonics: Satellite Data Compression, Communications and Archiving III, San Diego, CA, USA, SPIE, CD-ROM, 6683-07.

We describe how radar data is transmitted, compressed and archived. We note that although custom compression techniques have been devised for radar data that outperform generic techniques, radar operations groups ultimately use off-the-shelf solutions. We also point out that the underlying ideas behind compressibility are useful beyond just reducing the amount of data for transmission and archival. The compressibility of radar data has been found useful for devising quality control algorithms, especially for the detection and removal of test patterns.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/radarcompression.pdf.

Lakshmanan, V., K. Hondl, 2007: A polar-coordinate real-time three-dimensional rapidly updating merger technique for phased array radar scanning strategies. Proc. 33rd Conference on Radar Meteorology, Cairns, Australia, Amer. Meteor. Soc., CD-ROM, 7.4.

The National Weather Radar Testbed (NWRT) phased array radar will not be operated in fixed volume coverage patterns. Instead, the phased array radar will attempt to simultaneously maximize the utility of several possible uses, such as 3D storm analysis, area surveillance and aircraft tracking. In order to do so, the phased array radar will employ adaptive scanning and intersperse meteorological scans with aircraft tracking. To a downstream visualization program or automated severe-weather detection algorithm operating on phased array radar data, the incoming stream will be randomly organized in space and time. It is up to the application to create a coherent view of the atmosphere from the phased array radar beams.

In this paper, we describe a method of creating such a coherent view. In polar coordinates, this involves creating a rapidly updated "virtual volume scan". The virtual volume scan is created by treating each of the phased array radar range gates as "intelligent agents" that place themselves in the resulting polar grid, know how to collaborate with other agents to create optimal estimates of the radar values at each range gate of the virtual volume and know when they have either been superseded or are too old. The resulting virtual volume, created in real-time, is used by the downstream applications. This enables the downstream applications to work with a regularly spaced grid that is created at periodic intervals.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/polarmerger.pdf.

Lakshmanan, V., J. Zhang, C. Langston, 2008: Quality control of Canadian radar reflectivity data. Proc. European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Finnish Meteorological Institute, P2.11.

Lakshmanan, V., K. Hondl, R. Rabin, 2009: An efficient, general-purpose technique for identifying storm cells in geospatial images. Journal of Atmospheric and Oceanic Technology, 26, 523-537.

Existing techniques to identify, associate and track storms rely on
heuristics and are not transferrable between different types of
geospatial images. Yet, with the multitude of remote sensing
instruments and the number of channels and data types increasing, it
is necessary to develop a principled and generally applicable technique.
In this paper, an efficient, sequential, morphological technique
called the watershed transform is adapted and extended so that it can be used
for identifying storms. The parameters available
in the technique and the effect of these parameters are also explained.

The method is demonstrated
on different types of geospatial radar and satellite images.
Pointers are provided
on the effective choice of parameters
to handle the resolutions, data quality constraints
and dynamic range found in observational datasets.

Available online at http://cimms.ou.edu/~lakshman/Papers/localmax.pdf.

Lakshmanan, V., T. Smith, R. Rabin, 2008: Automated real-time extraction of storm properties from gridded fields. Preprints, Fifth European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Finnish Meteorological Institute, CD-ROM, CD-ROM.

A multiscale segmentation algorithm has been developed to identify storms at different scales through contiguity-enhanced K-Means clustering of texture features. The identified storms are used as a template for tracking storms through time and for identifying storm properties. A variety of scalar features are computed from the gridded values falling within the geographic and temporal extent of the identified clusters.

The resulting algorithm is illustrated in real-time operation and the utility of the extracted properties is demonstrated through a decision tree that is capable of identifying the storm type based on just the automatically extracted properties.

Available online at http://cimms.ou.edu/~lakshman/Papers/auto_storm_type.pdf.

Lakshmanan, V., E. Ebert, S. Haupt, 2008: `The 2008 artificial intelligence competition. Preprints, 6th Conference on Artificial Intelligence Applications to Environmental Science, New Orleans, LA, USA, Amer. Meteor. Soc., CD-ROM, 2.1.

Lakshmanan, V., R. Rabin, 2008: Nowcasting of thunderstorms from GOES infrared and visible imagery. Preprints, 5th GOES Users' Conference, New Orleans, LA, USA, Amer. Meteor. Soc, CD-ROM, P1.73.

Lakshmanan, V., T. Smith, 2009: Lighting warning and prediction using observations and models. Preprints, th Conference on the Meteorological Applications of Lightning Data,, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, 6.4.

Cloud-to-ground lightning data from the National Lightning Data Network (NLDN), satellite visible and radar-derived products are used to train a lightning prediction algorithm. The radar reflectivity values are clustered to identify storm and real-time geometric, lagrangian and scalar attributes of those storms are computed. A lightning density field is "precast" to form the target decision field to be predicted using the computed attributes. Several days of data from the continental United States were chosen to obtain a seasonally and geographically diverse dataset for training. The trained system is used to predict lightning density and the predicted lightning density field is advected to produce a 30-minute nowcast field. The skill of the resulting algorithm is evaluated against a steady-state prediction with motion correction.

Available online at http://cimms.ou.edu/~lakshman/Papers/ltgpred2009.pdf.

Lakshmanan, V., 2009: The Simpler the Better. Preprints, 6th Conference on Artificial Applications to the Environmental Sciences, Phoenix, AZ, USA, Amer. Meteo. Society, CD-ROM, CD-ROM.

Lakshmanan, V., J. J. Gourley, Z. Flamig, S. Giagrande, 2009: A simple data-driven model for streamflow prediction. Preprints, 6th Conference on Artificial Applications to the Environmental Sciences, Phoenix, AZ, USA, Amer. Meteor. So, CD-ROM, J6.2.

Lakshmanan, V., T. Smith, 2009: Data Mining Storm Attributes from Spatial Grids. Journal of Atmospheric and Oceanic Technology, 26, 2353-2365.

A technique to identify storms and capture scalar features within the geographic and temporal extent of the identified storms is described. The identification technique relies on clustering grid points in an observation field to find self-similar and spatially coherent clusters that meet the traditional understanding of what storms are. From these storms, geometric, spatial and temporal features can be extracted. These scalar features can then be data mined to answer many types of research questions in an objective, data-driven manner. This is illustrated by using the technique to answer questions of forecaster skill and lightning predictability.

Available online at http://cimms.ou.edu/~lakshman/Papers/stormattr.pdf.

Lakshmanan, V., J. Zhang, K. Howard, 2010: A Technique to Censor Biological Echoes in Radar Reflectivity Data. Journal of Atmospheric and Oceanic Technology, 49, 435-462.

Weather radar data is susceptible to several artifacts due to anamalous
propagation, ground clutter, electronic interference, sun angle,
second-trip echoes and biological contaminants such as insects, bats and
birds. Several methods of censoring radar reflectivity data have been devised
and described in the literature. However, they all rely on analyzing the
local texture and vertical profile of reflectivity fields.

The local texture of reflectivity fields suffices to remove most artifacts,
except for biological echoes. Biological echoes have proved difficult to remove
because they can have the same returned power and vertical profile
as stratiform rain or snow.

In this paper, we describe a soft-computing technique based on
clustering, segmentation and a two-stage neural network to censor
all non-precipitating artifacts in weather radar reflectivity data.
We demonstrate that the technique is capable of discrimination between
light snow, stratiform rain and deep biological "bloom".

Available online at http://cimms.ou.edu/~lakshman/Papers/qcnnbloom.pdf.

Lakshmanan, V., J. Kain, 2010: A Gaussian Mixture Model Approach to Forecast Verification. Weather and Forecasting, 25, 908-920.

Verification methods for high-resolution forecasts have been based either
on filtering or on objects created by thresholding the images.
The filtering methods do not easily permit the use of
deformation while identifying objects based on thresholds can be problematic.
In this paper, we introduce a new approach in which the
observed and forecast fields are broken down into a mixture of Gaussians, and
the parameters of the Gaussian Mixture Model fit are examined
to identify translation, rotation and scaling errors.
We discuss the advantages of this method in
terms of the traditional filtering or object-based methods and
interpret resulting scores on a standard verification dataset.

Available online at http://cimms.ou.edu/~lakshman/Papers/gmmverif.pdf.

Lakshmanan, V., T. Smith, 2010: An Objective Method of Evaluating and Devising Storm Tracking Algorithms. Weather and Forecasting, 25, 721-729.

We
introduce a set of
easily computable bulk statistics that
can be used to directly evaluate the performance of tracking algorithms
on specific characteristics.
We apply the evaluation method to a diverse set of radar reflectivity data
cases and note the characteristic behavior of five different storm
tracking algorithms proposed in the literature and now employed in widely
used nowcasting systems. Based on this objective evaluation, we devise
a storm tracking algorithm that performs consistently and better than any
of the previously suggested techniques.

Available online at http://cimms.ou.edu/~lakshman/Papers/scoretrack.pdf.

Lakshmanan, V., 2010: Extrapolating radar images using a Gaussian Mixture Model. Extended Abstracts, Sixth European Conference on Radar in Meteorology and Hydrology, Sibiu, Romania, National Meteorological Administration, Romania, CD-ROM, CDROM.

A new parametric approach to extrapolating geospatial images is introduced. The advantage of a parametric approach is that it can capture, besides the motion vector that all conventional techniques aim to estimate, aspects of change in size and shape of the echoes. A Gaussian Mixture Model (GMM) is used to approximate the weather data within the image. The transformation necessary to morph that GMM to best approximate the previous image in the sequence is determined. The reverse transformation (movement, change in size and shape) is then applied to the GMM to create extrapolation forecasts. We find that the technique performs as expected on synthetic sequences, but that more work needs to be done to carry out a fit of the GMM to real radar imagery.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/ERAD_gmm_extrapolation.pdf.

Lakshmanan, V., J. S. Kain, 2010: Model Verification Using Gaussian Mixture Models. Preprints, 20th Conference on Probability and Statistics in the Atmospheric Sciences, Atlanta, GA, USA, Amer. Meteor. Soc., 6.4.

Lakshmanan, V., J. Kain, 2010: A Gaussian mixture model approach to forecast verification. Weather and Forecasting, 25, 908-920.

We introduce a new approach in which the observed and forecast fields are broken down into a mixture of Gaussians and the parameters of the Gaussian Mixture Model fit are examined to identify translation, rotation and scaling errors. We discuss the advantages of this method in terms of the traditional filtering or object-based methods and interpret resulting scores on a standard verification dataset.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/gmmverif.pdf.

Lakshmanan, V., T. Smith, 2010: An objective method of evaluating and devising storm tracking algorithms. Weather and Forecasting, 25, 721-729.

We introduce a set of easily computable bulk statistics that can be used to directly evaluate the performance of tracking algorithms on specific characteristics. We apply the evaluation method to a diverse set of radar reflectivity data cases and note the characteristic behavior of five different storm tracking algorithms proposed in the literature and now employed in widely used nowcasting systems. Based on this objective evaluation, we devise a storm tracking algorithm that performs consistently and better than any of the previously suggested techniques.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/scoretrack.pdf.

Lakshmanan, V., K. Elmore, M. Richman, 2010: Reaching scientific consensus through a competition. Bulletin of the American Meteorological Society, 91, 1423-1427.

Lakshmanan, V., J. Zhang, K. Howard, 2010: A technique to censor biological echoes in radar reflectivity data. Journal of Applied Meteorology and Climatology, 49, 435-462.

we describe a technique that identifies candidate bloom based on the range-variance of reflectivity in areas of bloom, and uses the global, rather than local, characteristic of the echo to discriminate between bloom and wide-spread rain. Every range gate is assigned a probability that it corresponds to bloom using morphological operations and a neural network is trained using this probability as one of the input features. We demonstrate that this technique is capable of identifying and removing echoes due to biological targets and other types of artifacts while retaining echoes that correspond to precipitation.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/bloomjam.pdf.

Lakshmanan, V., 2010: Extrapolating radar images using a gaussian mixture model. Preprints, Sixth European Conference on Radar in Meteorology and Hydrology, Sibiu, Romania, National Meteorological Administration, Romania, CD-ROM, cd.

Lakshmanan, V., j. Kain, 2010: Model verification using gaussian mixture models. Extended Abstracts, 20th Conference on Probability and Statistics in the Atmospheric Sciences, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 6.4.

Lakshmanan, V., T. Smith, 2010: Evaluating a storm tracking algorithm. Preprints, 26th Conf. on IIPS for Meteo., Ocean. and Hydr., Atlanta, GA, USA, Amer. Meteor. Soc, CD-ROM, 8.2.

Lakshmanan, V., 2010: Predicting turbulence using partial least squares regression and an artificial neural network. Extended Abstracts, 7th Conference on Artificial Applications to the Environmental Sciences, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 3.3.

Lakshmanan, V., J. L. Cintineo, T. M. Smith, 2010: Performance of a Probabilistic Cloud-to-Ground Lightning Prediction Algorithm. Extended Abstracts, 20th Conference on Probability and Statistics in the Atmospheric Sciences, Atlanta, GA, USA, AMS, 526.

A probabilistic cloud-to-ground lightning algorithm was created by training a neural network on storm characteristics. The input dataset consisted of all storm cells over the entire coterminous United Stateson 12 days in 2008-2009 (one day per month). The input characteristics include radar and near-storm environmental parameters and the neural network was set up so that its output is the probability of cloud-to-ground lightning at a grid location 30 minutes in the future. The probabilistic output was evaluated on several independent test dates in 2009 and results of that evaluation are presented.

Available online at http://ams.confex.com/ams/90annual/techprogram/paper_162559.htm.

Lakshmanan, V., 2012: Automating the Analysis of Spatial Grids: A Practical Guide to Data Mining Geospatial Images for Human and Environmental Applications. Springer, 323 pp.

The ability to create automated algorithms to process gridded spatial data is increasingly important as remotely sensed datasets increase in volume and frequency. Whether in business, social science, ecology, meteorology or urban planning, the ability to create automated applications to analyze and detect patterns in geospatial data is increasingly important. This book provides students with a foundation in topics of digital image processing and data mining as applied to geospatial datasets. The aim is for readers to be able to devise and implement automated techniques to extract information from spatial grids such as radar, satellite or high-resolution survey imagery.

http://www.springer.com/engineering/signals/book/978-94-007-4074-7

Lakshmanan, V., R. Rabin, J. Otkin, J. Kain, 2012: Approximating radiative transfer with a neural network. Preprints, 10th Conf. on Artificial Intelligence App. to Env. Sci., Norman, OK, USA, AMS, CD-ROM, TJ14.3.

We demonstrate that it is possible to approximate the radiative transfer model using an universal approximator whose parameters can be determined by fitting the output of the forward model to inputs derived from the model forecasts from which it was computed. The resulting approximation is very close to the complex radiative transfer model and has the advantage that it can be computed in a matter of minutes. This approximation is carried out on model forecasts to demonstrate its utility as a visualization and forecasting tool.

Lakshmanan, V., 2011: Detecting convective inititation from radar. Preprints, International Symposium on Earth-science Challenges: 2nd Summit between the University of Oklahoma and Kyoto University, Norman, OK, USA, University of Oklahoma, 13-13.

On the process of detecting CI from a pair of radar images.

Lakshmanan, V., J. Crockett, M. Ba, K. Sperrow, L. Xin, 2011: Automated Way to Tune AutoNowCaster. Preprints, 10th Conf. on Artificial Intelligence App. to Env. Sci., New Orleans, LA, USA, AMS, CD-ROM, TJ14.1.

We use a genetic algorithm to tune AutoNowCaster, a fuzzy logic system. This involves creation of a ground truth convective initiation field

Lakshmanan, V., 2012: Image processing of weather radar reflectivity data: Should it be done in Z or dBZ?. EJSSM, 7, 1-4.

It appears to be a common belief that processing, such as interpolation,
clustering or
smoothing, of weather radar reflectivity fields ought to be carried out on
the reflectivity factor ($Z$) and not on its logarithm (dB$Z$). It is demonstrated
here by means of a statistical study on a large dataset
that, contrary to common belief,
processing in dB$Z$ is better for such applications.

Available online at http://cimms.ou.edu/~lakshman/Papers/zordbz.pdf.

Lakshmanan, V., R. Rabin, J. Kain, J. Otkin, S. Dembek, 2012: Visualizing Model Data Using A Fast Approximation of a Radiative Transfer Model. Journal of Atmospheric and Oceanic Technology, 29, 745-754.

Visualizing model forecasts using simulated satellite imagery has proven very useful because the depiction of forecasts using cloud imagery can provide inferences about meteorological scenarios and
physical processes that are not characterized well by depictions of those forecasts using radar reflectivity. A forward radiative transfer model is capable of providing such a visible-channel depiction of numerical weather prediction model output, but present-day forward models are too slow to run routinely on operational model forecasts.

It is demonstrated that it is possible to approximate the radiative transfer model using an universal approximator whose parameters can be determined by fitting the output of the forward model to inputs derived from the raw output from the prediction model. The resulting approximation is very close to the result derived from the complex radiative transfer model and has the advantage that it can be computed in a
small fraction of the time required by the forward model. This approximation is carried out on model forecasts to demonstrate its utility as a visualization and forecasting tool.

Available online at http://cimms.ou.edu/~lakshman/Papers/visnn.pdf.

Lakshmivarahan, S., J. M. Lewis, 2010: Forward Sensitivity Approach to Dynamic Data Assimilation. Advances in Meteorology, 2010, 1-13.

The least squares fit of observations with known error variance to a strong-constraint dynamical model has been developed through use of the time evolution of sensitivity functions – the derivatives of model output with respect to the elements of control (initial conditions, boundary conditions, and physical/empirical parameters). Model error is assumed to stem from incorrect specification of the control elements. The optimal corrections to control are found through solution to an inverse problem. Duality between this method and the standard 4D-Var assimilation using adjoint equations has been proved. The paper ends with an illustrative example based on a simplified version of turbulent heat transfer at the sea/air interface.

Lang, T. J., W. A. Lyons, S. A. Rutledge, J. D. Meyers, D. R. MacGorman, S. A. Cummer, 2010: Transient luminous events above two mesoscale convective systems: Storm structure and evolution. Journal Of Geophysical Research - Space, 115, A00E22.

Two warm‐season mesoscale convective systems (MCSs) were analyzed with respect to their production of transient luminous events (TLEs), mainly sprites. The 20 June 2007 symmetric MCS produced 282 observed TLEs over a 4 h period, during which the storm’s intense convection weakened and its stratiform region strengthened. TLE production corresponded well to convective intensity. The convective elements of the MCS contained normal‐polarity tripole charge structures with upper‐level positive charge (<−40°C), midlevel negative charge (−20°C), and low‐level positive charge near the melting level. In contrast to previous sprite studies, the stratiform charge layer involved in TLE production by parent positive cloud‐to‐ground (+CG) lightning resided at upper levels. This layer was physically connected to upper‐level convective positive charge via a downward sloping pathway. The average altitude discharged by TLE‐parent flashes during TLE activity was 8.2 km above mean sea level (MSL; −25°C). The 9 May 2007 asymmetric MCS produced 25 observed TLEs over a 2 h period, during which the storm’s convection rapidly weakened before recovering later. Unlike 20 June, TLE production was approximately anticorrelated with convective intensity. The 9 May storm, which also had a normal tripole in its convection, best fit the conventional model of low‐altitude positive charge playing the dominant role in sprite production; however, the average altitude discharged during the TLE phase of flashes still was higher than the melting level: 6.1 km MSL (−15°C). Based on these results, it is inferred that sprite production and sprite‐parent positive charge altitude depend on MCS morphology.

Lang, T. J., J. Li, W. A. Lyons, S. A. Cummer, S. A. Rutledge, D. R. MacGorman, 2011: Transient luminous events above two mesoscale convective systems: Charge moment change analysis. Journal of Geophysical Research: Space Science, 116, 1-11.

Charge moment change (ΔMQ) data were examined for 41 positive cloud‐to‐ground (+CG) lightning discharges that were parents of transient luminous events (TLEs; mainly sprites) over two different storms: 9 May (20 parents) and 20 June 2007 (21). Data were broken down by contributions from the impulse ΔMQ (iΔMQ), within the first 2 ms of the return stroke, and the ΔMQ from the continuing current (CC), which can last tens of ms afterward. Three‐dimensional lightning mapping data provided positions for the in‐cloud components of the parent +CGs. Charge and charge density neutralized by the strokes were estimated. The 20 June parents were more impulsive than 9 May, with increased iΔMQ and CC amplitude but reduced CC duration. Total ΔMQ values between the two storms were very similar, averaging approximately 1800 C km. Estimated charge density on 20 June was nearly twice that on 9 May, consistent with the 20 June storm being more intense with a stronger electrical generator. Lightning metrics were analyzed for 9 high‐ iΔMQ (>300 C km) +CGs that did not produce an observable TLE on 20 June, and compared to that day's TLE parents. Non‐TLE +CGs had reduced CC magnitudes and duration, with less total ΔMQ. Photogrammetric estimates of TLE azimuthal swaths were positively correlated with similar metrics of the in‐cloud portions of the parent +CGs, as well with total ΔMQ. The implications of all these results for the ΔMQ theory of sprite initiation, and for the relationship between sprite development and in‐cloud discharging, are discussed.

Langston, C., J. Zhang, K. Howard, 2007: Four-Dimensional Dynamic Radar Mosaic. Journal of Atmospheric and Oceanic Technology, 24, 776-790.

Le, K. D., R. D. Palmer, S. M. Torres, T.-Y. Yu, D. Zrnic, 2005: On the Use of Polarimetric Radars for Studies of Clouds: Numerical Simulations and S-Band Radar Observations. Preprints, 32nd International Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, 9R.7.

Le, K. D., R. D. Palmer, T. Y. Yu, G. Zhang, S. M. Torres, B. L. Cheong, 2007: Improving Angular Resolution Using Adaptive Processing for Multifunction Phased Array Radar. Preprints, 23rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, AMS, CD-ROM, P2.14A.

Le, K. D., R. D. Palmer, T. Y. Yu, G. Zhang, S. M. Torres, B. L. Cheong, 2007: Adaptive Array Processing for Multi-Mission Phased Array Radar. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P7.2.

As the use of phased array radars becomes more established for weather surveillance, adaptive array processing techniques will become more important to the weather radar community. Such techniques can be applied to phased array radars to improve angular resolution and also to suppress clutter compared to conventional beamforming methods. Thus, enhanced details of weather phenomena can be realized in terms of finer and better estimates of the reflectivity and radial velocity. This paper compares the performance of conventional beamforming to the performance of adaptive array processing based methods for a fully adaptive array and a partially adaptive array with six sidelobe-canceling elements, which is the configuration of the Phased Array Radar (PAR) of the National Weather Radar Testbed (NWRT) in Norman, Oklahoma. Different scenarios of fading clutter and clutter positions relative to the steering directions are considered. The simulated phased array concept uses a transmit beam that is wide in both angular directions to illuminate a large field of view and is thus termed an imaging radar . The receiver consists of individual antenna elements placed in a planar configuration. Time series signals for each antenna element are generated using a realistic radar simulator based on point-target scatterers, which flow and scatter according to a simulated environment produced from the Advanced Regional Prediction System (ARPS). Preliminary results show that, as expected, the performance of more sophisticated adaptive algorithms is better compared to conventional beamforming, both in terms of angular resolution and clutter suppression.

Available online at http://ams.confex.com/ams/pdfpapers/123304.pdf.

Le, K., R. Palmer, B. Cheong, T. Yu, G. Zhang, S. M. Torres, 2008: Novel Adaptive Beamforming Techniques for Atmospheric Imaging Radars. Preprints, 24rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, AMS, CD-ROM, 9A.5.

Le, K., R. Palmer, B. Cheong, T. Yu, G. Zhang, S. Torres, 2009: On the use of auxiliary receive channels for clutter mitigation with phased array weather radars. IEEE Trans. Geosci. Remote Sensing, 47, 272-284.

Le, K., R. Palmer, B. Cheong, T. Yu, G. Zhang, S. Torres, 2008: Clutter Mitigation using Auxiliary Elements for the NWRT Phased Array Radar. Proc. European Radar Conference (EuRAD), Amsterdam, Netherlands, European Microwave Association, CD-ROM, R11.

Le, K., R. Palmer, B. Cheong, T. Yu, G. Zhang, S. Torres, 2010: Reducing the effects of noise on atmospheric imaging radars using multilag correlation. Radio Science, 45, .

Lengyel, M. M., H. E. Brooks, R. L. Holle, M. A. Cooper, 2005: Lightning casualties and their proximity to surrounding cloud-to-ground lightning. Preprints, 14th Symposium on Education, San Diego, CA, USA, American Meteorological Society, CD-ROM, P1.35.

Lengyel, M., M. A. Cooper, R. Holle, H. E. Brooks, 2010: The role of multidisciplinary teams and public education in reducing lightning casualties worldwide. Proc. 30th International Conference on Lightning Protection, Cagliari, Italy, IEEE, SSB-1329. [Available from macooper@uic.edu,

In the past century, lightning killed more people in the United States on average annually than any other storm situation except floods. However, due to persistent lightning safety efforts by a multidisciplinary team, the annual National Lightning Safety Awareness Week campaign, shifts in population from rural to urban areas, and improved grounding of buildings, US lightning deaths have decreased to an average of less than 50 per year over the past decade. This demonstrates that aggressive public education can have a significant role in reducing lightning deaths and injuries.

Lewis, J. M., D. Martin, R. Rabin, H. Moosmuller, 2010: Suomi: Pragmatic Visionary. Bulletin of the American Meteorological Society, 91, 561-577.

The steps on Verner Suomi's path to becoming a research scientist are examined. We argue that his research style – his natural interests in science and engineering, and his methodology in pursuing answers to scientific questions – was developed in his youth on the Iron Range of northeastern Minnesota, as an instructor in the cadet program at the University of Chicago (U of C) during World War II and as a fledgling academician at University of Wisconsin - Madison. We examine several of his early experiments that serve to identify his style. The principal results of the study are: 1) despite austere living conditions on the Iron Range during the Great Depression, Suomi benefitted from excellent industrial arts courses at Eveleth High School; 2) with his gift for designing instruments, his more practical approach to scientific investigation flourished in the company of world-class scientific thinkers at U of C; 3) his dissertation on the heat budget over a cornfield in the mid-1950s served as a springboard for studying the Earth-atmosphere energy balances in the space-age environment of the late 1950s; and 4) his design of radiometers – the so-called ping-pong radiometer and its sequel, the hemispheric bolometer – flew aboard Explorer VI and VII in the late 1950s, and analysis of the radiances from these instruments led to the first accurate estimate of the Earth's mean albedo.

Lewis, J. M., M. L. Kaplan, R. K. Vellore, R. M. Rabin, J. Hallett, S. A. Cohn, 2011: Dust Storm over the Black Rock Desert: Larger-scale Dynamic Signatures. Journal of Geophysical Research - D: Atmospheres, 116, 1-23.

A dust storm that originated over the Black Rock Desert (BRD) of northwestern Nevada is investigated. Our primary goal is to more clearly understand the sequence of dynamical processes that generate surface winds responsible for entraining dust from this desert. In addition to reliance on conventional surface and upper-air observations, we make use of reanalysis datasets (NCAR/NCEP and NARR) — blends of primitive equation model forecasts and observations. From these datasets, we obtain the evolution of vertical motion patterns and ageostrophic motions associated with the event. In contrast to earlier studies that have emphasized the importance of indirect transverse circulations about an upper-level jet streak, our results indicate that the transition from indirect to direct circulation across the exit region of upper-level jet streak is central to creation of low-level winds that ablate dust from the desert. It is further argued that the transition of vertical circulation patterns is in response to adjustments to geostrophic imbalance — where the adjustment time scale is the order of 6-9 h. Although unproven, we suggest that precedent rainfall over the alkali desert two weeks prior to the event was instrumental in lowering the bulk density of sediments and thereby improved the chances for dust ablation. We comprehensively compare/contrast our results with those of earlier investigators, and we present an alternative view of key dynamical signatures in atmospheric flow that portend the likelihood of dust storms over the western United States.

Li, Y., G. Zhang, R. J. Doviak, 2009: Crossbeam Wind Measurements using Spaced-Antenna and Doppler Beam Swinging Based on Monopulse Configurations with the National Weather Radar Testbed. P2.1. , January.. Extended Abstracts, AMS 89th Annual Conference, Phoenix, AZ, USA, AMS, 1-4.

Liao, Z., Y. Hong, D. Kirschbaum, R. Adler, J. J. Gourley, R. Wooten, 2011: Evaluation of TRIGRS (Transient Rainfall Infiltration and Grid-based Regional Slope-Stability Analysis)’s predictive skill for hurricane-triggered landslides: A case study in Macon County, North Carolina. Natural Hazards, 58, 325-339.

Liu, S., C. Qiu, Q. Xu, P. Zhang, J. Gao, A. Shao, 2005: An improved method for Doppler wind and thermodynamic retrievals. Advances in Atmospheric Sciences, 22, 90-102.

Liu, S., Q. Xu, P. Zhang, 2005: Quality control of Doppler velocities contaminated by migrating birds. Part II: Bayes identification and probability tests. Journal of Atmospheric and Oceanic Technology, 22, 1114-1121.

Liu, L., P. Zhang, Q. Xu, F. Kong, S. Liu, 2005: Retrieval model of dual linear polarization radar observations from simulation model output. Adv. Atmos. Sci. 22, 711-719., 22, 711-719.

Liu, L., Q. Xu, P. Zhang, S. Liu, 2008: Automated Detection of Contaminated Radar Image Pixels in Mountain Areas. Adv. Atmos. Sci., 25, 778-790.

In mountain areas, radar observations are often contaminated (1) by echoes from high-speed moving vehicles and (2) by point-wise ground clutter under either normal propagation (NP) or anomalous propagation (AP) conditions. Level II data are collected from KMTX (Salt Lake City, Utah) radar to analyze these two types of contamination in the mountain area around the Great Salt Lake. Human experts provide the ``ground truth" for possible contamination of either type on each individual pixel. Common features are then extracted for contaminated pixels of each type. For example, pixels contaminated by echoes from high-speed moving vehicles are characterized by large radial velocity and spectrum width. Echoes from a moving train tend to have larger velocity and reflectivity but smaller spectrum width than those from moving vehicles on highways. These contaminated pixels are only seen in areas of large terrain gradient (in the radial direction along the radar beam). The same is true for the second type of contamination - point-wise ground clutters. Six quality control (QC) parameters are selected to quantify the extracted features. Histograms are computed for each QC parameter and grouped for contaminated pixels of each type and also for non-contaminated pixels. Based on the computed histograms, a fuzzy logical algorithm is developed for automated detection of contaminated pixels. The algorithm is tested with KMTX radar data under different (clear and rainy) weather conditions.

Liu, S., G. DiMego, K. V. Kumar, D. Keyser, S. Guan, Q. Xu, K. Nai, P. Zhang, L. Liu, J. Zhang, X. Xu, K. Howard, 2009: WSR-88D radar data processing at NCEP. Extended Abstracts, 34rd Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, 14.2.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_156011.htm.

Liu, L., Y. Hong, J. Hocker, M. Shafer, L. Carter, J. Gourley, C. Bednarczyk, B. Yong, P. Adhikari, 2012: Analyzing projected changes and trends of temperature and precipitation in the southern USA from 16 downscaled global climate models. Theoretical and Applied Climatology, 0177-798X, 1-16.

This study aims to examine how future climate, temperature and precipitation specifically, are expected to change under the A2, A1B, and B1 emission scenarios over the six states that make up the Southern Climate Impacts Planning Program (SCIPP): Oklahoma, Texas, Arkansas, Louisiana, Tennessee, and Mississippi. SCIPP is a member of the National Oceanic and Atmospheric Administration- funded Regional Integrated Sciences and Assessments net- work, a program which aims to better connect climate-related scientific research with in-the-field decision-making processes. The results of the study found that the average temperature over the study area is anticipated to increase by 1.7°C to 2.4°C in the twenty-first century based on the different emission scenarios with a rate of change that is more pronounced during the second half of the century. Summer and fall seasons are projected to have more significant temperature increases, while the northwestern portions of the region are projected to experience more significant increases than the Gulf coast region. Precipitation projections, conversely, do not exhibit a discernible upward or downward trend. Late twenty-first century exhibits slightly more precipitation than the early century, based on the A1B and B1 scenario, and fall and winter are projected to become wetter than the late twentieth century as a whole. Climate changes on the city level show that greater warming will happened in inland cities such as Oklahoma City and El Paso, and heavier precipitation in Nashville. These changes have profound implications for local water resources man- agement as well as broader regional decision making. These results represent an initial phase of a broader study that is being undertaken to assist SCIPP regional and local water planning efforts in an effort to more closely link climate modeling to longer-term water resources management and to continue assessing climate change impacts on regional hazards management in the South.

Lu, G., S. A. Cummer, J. Li, W. A. Lyons, P. R. Krehbiel, W. Rison, R. J. Thomas, O. van der Velde, M. B. Cohen, T. L. Lang, S. A. Rutledge, W. H. Beasley, D. R. MacGorman, 2011: Lightning development associated with two gigantic jets. Geophysical Research Letters, 38, L12801.

We report observations of two negative polarity gigantic jets sufficiently near very high‐frequency (VHF) lightning mapping networks that the associated lightning characteristics and charge transfer could be investigated. In both cases the gigantic jet‐producing flash began as ordinary intracloud lightning with upper level channels attempting to exit the cloud, and then produced the upward gigantic jet. Neither flash had developed channels to ground, confirming that the major charge transfer during gigantic jets occurred between the cloud and ionosphere. The leader progression of one event was detected at altitudes above 20 km, demonstrating the possibility of detecting and tracking the propagation of negative jets above the cloud with VHF techniques.

Lund, N., D. MacGorman, D. Rust, T. Schuur, P. Krehbiel, W. Rison, T. Hamlin, J. Straka, M. Biggerstaff, 2007: Relationship between lightning location and polarimetric radar signatures in an MCS. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, IUGG/Commission on Atmospheric Electricity, PS5-2.

The relationship of lightning initiation and structure to the storm microphysics and structure depicted by polarimetric radar has been analyzed for a small mesoscale convective system (MCS) that occurred on 19 June 2004 during the Thunderstorm Electrification and Lightning Experiment (TELEX). Horizontal reflectivity (Z), differential reflectivity (Zdr), specific differential phase (Kdp) and correlation coefficient (ρHV) data were gathered by a 10-cm, polarimetric radar located in Norman, Oklahoma. Three-dimensional lightning structure was mapped by the Oklahoma Lightning Mapping Array (OK-LMA), and ground strike points were mapped by the United States National Lightning Detection Network. OK-LMA data were processed to group mapped points into flashes and to determine the initiation location of each flash that contained more than 10 mapped points. The initiation location was calculated by sequentially eliminating outliers among the first 10 points that occurred in a flash, with no fewer than 5 points being used in the final initiation location. The initiation location and mapped points for each flash were superimposed on polarimetric radar data in order to investigate lightning relationships with storm structure. The lightning initiation points tended to cluster together in one of two altitude ranges and were almost all in the convective line. Initial results show a relationship between the lightning initiation locations and radar signatures in both Z and Kdp. In the lower altitude range, between 3 and 5 km MSL, initiation locations tended to cluster around updraft cores, in regions characterized by a transition in Z from 50 to 55 dBZ and a transition in Kdp from 0.4 to 0.5 deg/km. In the upper range, between 8 and 10 km MSL, initiation points tended to cluster directly above the updrafts, in regions characterized by a transition in Z from 42.5 to 47.5 dBZ and in Kdp from 0.075 to 0.150 deg/km. The two-layer nature of the initiation points is consistent with grossly tripolar structure of the charge distribution involved in lightning in the convective line. Also, the horizontal pattern of the initiation locations has a quasi-periodic horizontal structure which is 180 degrees out of phase with the maximum updraft locations for the lower region and is in phase with the maximum updraft locations for the upper region. There were also a few flash initiations within the stratiform region, possibly associated with decaying cells. The values of Z and Kdp associated with these initiation points were smaller than in the convective line, but as in the convective line, the initiations also occurred along gradients, above a local maximum, in these parameters.

Lund, N., D. R. MacGorman, W. D. Rust, T. J. Schuur, P. Krehbiel, W. Rison, T. Hamlin, J. Straka, M. Biggerstaff, 2008: Relationship between lightning location and polarimetric radar signatures in an MCS. Preprints, 3rd Conference on Meteorological Applications of Lightning Data, New Orleans, LA, USA, American Meteorological Society, P1.5.

Lund, N. R., D. R. MacGorman, T. J. Schuur, M. I. Biggerstaff, W. D. Rust, 2009: Relationships between Lightning Location and Polarimetric Radar Signatures in a Small Mesoscale Convective System. Monthly Weather Review, 137, 4151-4170.

On 19 June 2004, the Thunderstorm Electrification and Lightning Experiment observed electrical, microphysical, and kinematic properties of a small mesoscale convective system (MCS). The primary observing systems were the Oklahoma Lightning Mapping Array, the KOUN S-band polarimetric radar, two mobile C-band Doppler radars, and balloon-borne electric field meters. During its mature phase, this MCS had a normal tripolar charge structure (lightning involved a midlevel negative charge between an upper and a lower positive charge), and flash rates fluctuated between 80 and 100 flashes per min. Most lightning was initiated within one of two altitude ranges (3-6 km MSL or 7-10 km MSL) and within the 35 dBZ contours of convective cells embedded within the convective line. The properties of two such cells were investigated in detail, the first lasting approximately 40 min and producing only 12 flashes and the second lasting over an hour and producing 105 flashes. In both, lightning was initiated in or near regions containing graupel. The upper lightning initiation region (7-10 km MSL) was near 35-47.5 dBZ contours, with graupel inferred below and ice crystals inferred above. The lower lightning initiation region (3-6 km MSL) was in the upper part of melting or freezing layers, often near differential reflectivity columns extending above the 0 deg C isotherm, which is suggestive of graupel formation. Both lightning initiation regions are consistent with what is expected from the noninductive graupel-ice thunderstorm electrification mechanism, though inductive processes may also have contributed to initiations in the lower region.

MacGorman, D., D. Rust, T. Schuur, M. Biggerstaff, J. Straka, C. Ziegler, E. Mansell, P. Krehbiel, W. Rison, T. Hamlin, L. Carey, E. Bruning, K. Kuhlman, N. Ramig, C. Payne, 2005: Lightning Relative to Storm Structure and Microphysics in TELEX. Polarimetric radar and electrical structure of a multicell storm. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 10R.7.

MacGorman, D. R., T. Filiaggi, R. L. Holle, R. A. Brown, 2007: Negative Cloud-to-Ground Lightning Flash Rates Relative to VIL, Maximum Reflectivity, Cell Height, and Cell Isolation. Journal of Lightning Research, 1, 132-147.

This study relates storm cell parameters derived automatically from the Doppler radars of the United States National Weather Service to negative cloud-to-ground lightning activity detected by the United States National Lightning Detection Network. Data from the central United States were processed for over 1200 cells from seventeen days. Each cell’s maximum ground flash rate was compared to a subjective rating of the degree of cell isolation and to three radar-derived cell parameters: maximum reflectivity, maximum vertically integrated liquid (VIL), and the maximum vertical thickness having at least 30 dBZ reflectivity above the 0 deg C isotherm (similar to 30-dBZ cell height). Of the three parameters, the maximum 30-dBZ thickness of cells had the most useful relationship: The mean and modal values of ground flash rates increased with increasing 30-dBZ thickness, and the mean and modal values of 30-dBZ thickness increased with increasing flash rates. However, large ground flash rates provided a better diagnostic for large 30-dBZ thickness than large 30-dBZ thickness provided for large ground flash rates. The degree of cell isolation and the complexity of cell evolution also had a large effect: Cells which were less isolated or whose evolution was more complex were more likely to produce a ground flash and larger ground flash rates. Besides effects of storm complexity and size suggested by previous investigators, we suggest that the more complex charge distribution produced by having older cells nearby improves a cell’s probability of access to the lower positive charge typically needed to initiate negative ground flashes.

MacGorman, D., K. Kuhlman, D. Rust, M. Biggerstaff, T. Schuur, J. Straka, P. Krehbiel, B. Rison, L. Carey, 2007: Lightning and electrical structure of a heavy-precipitation supercell storm during TELEX. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, IUGG/Commission on Atmospheric Electricity, OS5-1.

The Thunderstorm Electrification and Lightning Experiment (TELEX) observed a heavy-precipitation (HP) supercell storm in central Oklahoma on 29 May 2004. In a HP supercell storm, the initial location of the mesocyclone, which is the parent rotation of tornadoes, is embedded well within the precipitation of the storm, instead of being on the edge of the storm (as in classic and low-precipitation supercell storms). Two 5-cm wavelength mobile Doppler radars were positioned near the storm and collected volume scans every 3 minutes for 3 h beginning as the storm became supercellular. The storm had supercell characteristics for this entire period. The Oklahoma Lightning Mapping Array provided three-dimensional data throughout the storm’s supercellular stage and provided two-dimensional data from the time of storm initiation in western Oklahoma. A 10-cm wavelength polarimetric radar also provided data for much of this period.
Lightning flash rates became extraordinarily large as the storm evolved into a supercell and its motion turned rightward. Flash rates increased again (to an estimated peak value of almost 500 flashes per minute) shortly before the storm produced a tornado rated F2 on the Fujita scale. During this period, an upward pulse in lightning density extended as high as 18 km MSL in a plume extending above the equilibrium level, and the region of lightning activity pulsed eastward far into the anvil, up to 150 km from the western edge of the storm. A series of minimums in the plan projection of lightning density (i.e., lightning holes) formed just above the bounded weak echo region. A dual-Doppler synthesis of wind during one volume scan shows the lightning hole was co-located with large vertical wind speeds in the rotating updraft. The hole apparently occurred because precipitation particles had little time to grow and gain charge in the strong updraft before they were lifted to upper regions of the storm and advected outward by flow from the diverging updraft. Cloud-to-ground lightning activity in and near heavy precipitation was dominated initially by negative ground flashes, but during part of the supercell phase, evolved to become dominated by positive ground flashes. Lightning mapping data suggest that, when positive ground flashes dominated, the vertical polarity of the storm’s electrical structure was inverted from the usual polarity.

MacGorman, D., C. L. Ziegler, E. Mansell, W. Beasley, B. Fiedler, 2005: Retrieval and assimilation of storm characteristics from both in-cloud and cloud-to-ground lightning data to improve mesoscale model forecasts. Final report to the Office of Naval Research (ONR Grant # N00014-00-1-0525) 1, 54 pp.

MacGorman, D. R., W. D. Rust, T. J. Schuur, M. I. Biggerstaff, J. M. Straka, C. L. Ziegler, E. R. Mansell, E. C. Bruning, K. M. Kuhlman, N. R. Lund, N. S. Biermann, C. Payne, L. D. Carey, P. R. Krehbiel, W. Rison, K. B. Eack, W. H. Beasley, 2008: TELEX: The Thunderstorm Electrification and Lightning Experiment. Bulletin of the American Meteorological Society, 89, 997-1013.

The field program of the Thunderstorm Electrification and Lightning Experiment (TELEX) took place in central Oklahoma, May–June 2003 and 2004. It aimed to improve understanding of the interrelationships among microphysics, kinematics, electrification, and lightning in a broad spectrum of storms, particularly squall lines and storms whose electrical structure is inverted from the usual vertical polarity. The field program was built around two permanent facilities: the KOUN polarimetric radar and the Oklahoma Lightning Mapping Array. In addition, balloon-borne electric-field meters and radiosondes were launched together from a mobile laboratory to measure electric fields, winds, and standard thermodynamic parameters inside storms. In 2004, two mobile C-band Doppler radars provided high-resolution coordinated volume scans, and another mobile facility provided the environmental soundings required for modeling studies. Data were obtained from twenty-two storm episodes, including several small isolated thunderstorms, mesoscale convective systems, and supercell storms. Examples are presented from three storms. A heavy-precipitation supercell storm on 29 May 2004 produced greater than 3 flashes per second for 1.5 h. Holes in the lightning density formed and dissipated sequentially in the very strong updraft and bounded weak echo region of the mesocyclone. In a small squall line on 19 June 2004, most lightning flashes in the stratiform region were initiated in or near strong updrafts in the convective line and involved positive charge in the upper part of the radar bright band. In a small thunderstorm on 29 June 2004, lightning activity began as polarimetric signatures of graupel first appeared near lightning initiation regions.

Available online at http://ams.allenpress.com/archive/1520-0477/89/7/pdf/i1520-0477-89-7-997.pdf.

MacGorman, D. R., T. Mansell, C. Ziegler, J. Straka, 2008: Detailed storm simulations by a numerical cloud model with electrification and lightning parameterizations. Preprints, 20th International Lightning Detection Conference, Tucson, AZ, USA, Vaisala, 28.

We have further developed our three-dimensional cloud model, which includes parameterizations of lightning, corona from ground, ion production and capture, and inductive and noninductive electrification mechanisms, as well as advanced treatments of advection, microphysics, and dynamics. Our most recent improvements have been to improve the model's treatment of microphysics, particularly particle size distributions. This model has been used to simulate many types of storms, from small isolated storms to extensive storm systems, supercell storms, and an idealized hurricane, with excellent similitude to observed kinematic structure in many cases. We will show examples of our simulations and will discuss relationships among the model fields, particularly between lightning and other storm properties. Lightning usually is correlated with precipitation ice mass and with the mass flux through the mixed phase region for updrafts >10 m/s.

MacGorman, D., T. Schuur, M. Kumjian, 2008: Total lightning activity during the re-intensification of Tropical Storm Erin over Oklahoma on 18–19 August 2007. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, 7A.5.

The remnants of Tropical Storm Erin made landfall on the Texas coast on 16 August 2007 and reached Oklahoma on 18 August, where it produced tornadoes, severe straight-line winds, and flooding. In west-central Oklahoma (roughly 800 km from the coast), the system re-intensified and formed an eye and rainband structure characteristic of tropical cyclones. The Oklahoma Mesonet indicated that the system eventually produced greater sustained winds (26 m s-1, 58 mph) and a lower central pressure (1001.3 hPa) than it had produced over open water.

The eye, which fluctuated from 5 to 25 km in diameter, was first apparent on lightning and radar displays at 4:50 am local time and began dissipating over Oklahoma City at 9:50 am. Throughout the period during which the eye formed and dissipated, the eye and the majority of the area of rainbands were well within the region in which the Oklahoma Lightning Mapping Array maps lightning in three dimensions and in which the KOUN S-Band radar provides polarimetric data. Both radar displays and displays of lightning density delineated the formation of the eye and rainband well. Convection extended highest and lightning rates were greatest in the rainband on the southeast flank. The height of convection in the rainband decreased as one approached the eye, and the decrease in height extended around the eye as the eye formed. Some long, horizontal flashes extended eastward from storms along the east side of the eye into the region of widespread light precipitation east of the rainband. The appearance of these long horizontal flashes was similar to the lightning structure observed in the stratiform precipitation regions of mesoscale convective systems. As the cyclone structure weakened, convection on the west side of the eye dissipated, and the remnants of the rainband on the east side propagated eastward as a line of storms.

Though the lightning in this system was probably influenced by being over land, this case still may provide clues to what happens electrically in tropical cyclones over open water, where continuous observations of total lightning activity during tropical cyclone intensification and dissipation are not yet available.

Available online at http://www.ametsoc.org.

MacGorman, D., C. Ziegler, T. Mansell, J. Straka, P. Krehbiel, B. Rison, T. Hamlin, 2005: Applications of advanced lightning mapping technologies to storm research and weather operations. Preprints, Conference on Meteorological Applications of Lightning Data, San Diego, CA, USA, American Meteorological Society, 2.1.

MacGorman, D. R., W. D. Rust, C. L. Ziegler, T. J. Schuur, E. R. Mansell, M. I. Biggerstaff, J. M. Straka, E. C. Bruning, K. M. Kuhlman, N. R. Ramig, C. D. Payne, N. S. Biermann, P. R. Krehbiel, W. Rison, T. Hamlin, L. D. Carey, 2005: Lightning relative to storm structure, evolution, and microphysics in TELEX. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, 10R.7.

Mansell, E. R., D. R. MacGorman, C. L. Ziegler, J. M. Straka, 2005: Charge structure in a simulated multicell thunderstorm. Journal of Geophysical Research, 110, .

A three-dimensional dynamic cloud model is used to investigate electrification of the full life cycle of an idealized continental multicell storm. Five laboratory-based parameterizations of noninductive graupel-ice charge separation are compared. Inductive (i.e., electric field-dependent) charge separation is tested for rebounding graupel-droplet collisions. Each noninductive graupel-ice parameterization is combined with variations in the effectiveness of inductive charging (off, moderate, and strong) and in the minimum ice crystal concentration (10 or 50/L). Small atmospheric ion processes such as hydrometeor attachment and point discharge at the ground are treated explicitly. Three of the noninductive schemes readily produced a normal polarity charge structure, consisting of a main negative charge region with an upper main positive charge region and a lower positive charge region. Negative polarity cloud-to-ground (CG) flashes occurred when the lower positive charge (LPC) region had sufficient charge density to cause high electric fields. Two of the three also produced one or more +CG flashes. The other two noninductive charging schemes, which are dependent on the graupel rime accretion rate, tended to produce an initially inverted polarity charge structure and +CG flashes. The model results suggest that inductive graupel-droplet charge separation could play a role in the development of lower charge regions. Noninductive charging, on the other hand, was also found to be capable of producing strong lower charge regions in the tests with a minimum ice crystal concentration of 50/L.

Mansell, T., C. Ziegler, D. MacGorman, 2006: A Lightning Data Assimilation Technique for Mesoscale Forecast Models. Preprints, 1st International Lightning Meteorology Conference, Tucson, AZ, USA, Vaisala, CD-ROM, N/A. [Available from Vaisala, Inc., Tucson Operations, 2705 E. Medina Rd., Tucson, AZ, USA, 85706.]

Lightning observations have been assimilated into the COAMPS mesoscale model for improvement of forecast initial conditions. Data are used from the National Lightning Detection Network (NLDN, cloud-to-ground lightning detection) and a Lightning Mapping Array (LMA; total lightning detection) that was installed in western Kansas/eastern Colorado. The assimilation method uses lightning as a proxy for the presence or absence of deep convection. During assimilation, lightning data are used to control the Kain-Fritsch (KF) convection parameterization scheme (CPS). The KF scheme can be forced to try to produce convection where lightning indicated storms, and, conversely, can optionally be prevented from producing spurious convection where no lightning was observed. Up to 1 g/kg of water vapor may be added to the boundary layer when the KF convection is too weak. The method does not make any use lightning-rainfall relationships, rather allowing the KF scheme to generate heating and cooling rates from its modeled convection. The method could therefore be used easily for real-time assimilation of any source of lightning observations.

Results will be presented for a warm-season test case 20-21 July 2000, when storms initiated and developed in large systems in Kansas both days. The second round of convection began by 22:00 UTC (20 July), and storm system with strong outflow had developed by 00 UTC on 21 July. Lightning data were assimilated over a 24 hour period (starting at 00 UTC on 20 July), covering the first round of convection and the start of the second. A control run was spun up over the same period only with the usual 12-hourly update cycle. As expected, during the assimilation period the model produces substantially more accurate precipitation (rates and location) than the control forecast. Even when water vapor was added to enhance convection, the rainfall rates were generally less than those indicated by rain gauge data. A forecast was started from the resulting initial condition at 00 UTC on 21 July 2000.

The lightning assimilation was successful in generating the cold pool that was present in the surface observations at initialization of the forecast. The resulting forecast showed considerably more skill than the control forecast, especially in the first few hours as convection was triggered by the propagation of the cold pool boundary.

Mansell, E. R., C. L. Ziegler, D. R. MacGorman, 2006: A Lightning Data Assimilation Technique for Mesoscale Forecast Models. Preprints, Second Conference on Meteorological Applications of Lightning Data, Atlanta, GA, USA, American Meteorological Society, 4.2.

Lightning observations have been assimilated into the COAMPS mesoscale model for improvement of forecast initial conditions. Data are used from the National Lightning Detection Network (NLDN, cloud-to-ground lightning detection) and a Lightning Mapping Array (LMA; total lightning detection) that was installed in western Kansas/eastern Colorado. The assimilation method uses lightning as a proxy for the presence or absence of deep convection. During assimilation, lightning data are used to control the Kain-Fritsch (KF) convection parameterization scheme (CPS). The KF scheme can be forced to try to produce convection where lightning indicated storms, and, conversely, can optionally be prevented from producing spurious convection where no lightning was observed. Up to 1 g/kg of water vapor may be added to the boundary layer when the KF convection is too weak. The method does not make any use lightning-rainfall relationships, rather allowing the KF scheme to generate heating and cooling rates from its modeled convection. The method could therefore be used easily for real-time assimilation of any source of lightning observations.

Results will be presented for a warm-season test case 20-21 July 2000, when storms initiated and developed in large systems in Kansas both days. The second round of convection began by 22:00 UTC (20 July), and storm system with strong outflow had developed by 00 UTC on 21 July. Lightning data were assimilated over a 24 hour period (starting at 00 UTC on 20 July), covering the first round of convection and the start of the second. A control run was spun up over the same period only with the usual 12-hourly update cycle. As expected, during the assimilation period the model produces substantially more accurate precipitation (rates and location) than the control forecast. Even when water vapor was added to enhance convection, the rainfall rates were generally less than those indicated by rain gauge data. A forecast was started from the resulting initial condition at 00 UTC on 21 July 2000.

The lightning assimilation was successful in generating the cold pool that was present in the surface observations at initialization of the forecast. The resulting forecast showed considerably more skill than the control forecast, especially in the first few hours as convection was triggered by the propagation of the cold pool boundary.

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_104180.htm.

Mansell, E. R., C. L. Ziegler, D. R. MacGorman, 2007: A Lightning Data Assimilation Technique for Mesoscale Forecast Models. Monthly Weather Review, 135, 1732-1748.

Lightning observations have been assimilated into a mesoscale model for improvement of forecast initial conditions. Data are used from the National Lightning Detection Network (cloud-to-ground lightning detection) and a Lightning Mapping Array (total lightning detection) that was installed in western Kansas–eastern Colorado. The assimilation method uses lightning as a proxy for the presence or absence of deep convection. During assimilation, lightning data are used to control the Kain–Fritsch (KF) convection parameterization scheme. The KF scheme can be forced to try to produce convection where lightning indicated storms, and, conversely, can optionally be prevented from producing spurious convection where no lightning was observed. Up to 1 g/kg of water vapor may be added to the boundary layer when the KF convection is too weak. The method does not employ any lightning–rainfall relationships, but rather allows the KF scheme to generate heating and cooling rates from its modeled convection. The method could therefore easily be used for real-time assimilation of any source of lightning observations. For the case study, the lightning assimilation was successful in generating cold pools that were present in the surface observations at initialization of the forecast. The resulting forecast showed considerably more skill than the control forecast, especially in the first few hours as convection was triggered by the propagation of the cold pool boundary.

Mansell, E., C. L. Ziegler, E. Bruning, 2007: Simulated electrification of a TELEX multicell storm. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, International Commission on Atmospheric Electricity, 290-293.

Mansell, E. R., C. L. Ziegler, E. C. Bruning, 2010: Simulated electrification of a small thunderstorm with two-moment bulk microphysics. Journal of the Atmospheric Sciences, 67, 171-194.

Electrification and lightning are simulated for a small continental multicell storm. The results are consistent with observations and thus provide additional understanding of the charging processes and evolution of this storm. The first six observed lightning flashes were all negative cloud-to ground (CG) flashes, after which intracloud (IC) flashes also occurred between middle and upper levels of the storm. The model simulation reproduces the basic evolution of lightning from low and middle levels to upper levels. The observed lightning indicated an initial charge structure of at least an inverted dipole (negative charge above positive). The simulations show that noninductive charge separation higher in the storm can enhance the main negative charge sufficiently to produce negative CG flashes before upper level IC flashes commence. The result is a ‘‘bottom-heavy’’ tripole charge structure with midlevel negative charge and a lower positive charge region that is more significant than the upper positive region, in contrast to the traditional tripole structure that has a less significant lower positive charge region. Additionally, the occurrence of cloud-to-ground lightning is not necessarily a result of excess net charge carried by the storm, but it is primarily caused by the local potential imbalance between the lowest charge regions.

The two-moment microphysics scheme used for this study predicted mass mixing ratio and number concentration of cloud droplets, rain, ice crystals, snow, and graupel. Bulk particle density of graupel was also predicted, which allows a single category to represent a greater range of particle characteristics. (An additional hail category is available but was not needed for the present study.) The prediction of hydrometeor number concentration is particularly critical for charge separation at higher temperatures (-5 < T < -20 deg C) in the mixed phase region, where ice crystals are produced by rime fracturing (Hallett–Mossop process) and by splintering of freezing drops. Cloud droplet concentration prediction also affected the rates of inductive charge separation between graupel and droplets.

Available online at http://journals.ametsoc.org/doi/pdf/10.1175/2009JAS2965.1.

Mansell, E. R., C. L. Ziegler, 2011: CCN Effects on Simulated Storm Electrification and Precipitation. Extended Abstracts, 18th Conf. Planned and Inadvertent Weather Modification, Seattle, WA, USA, Amer. Met. Soc., J15.2.

The effects of concentration of cloud condensation nuclei (CCN) on cloud microphysics have long been recognized, but the resultant effects on storm electrification are relatively unexplored. In the present study, a high-resolution 3D model is employed with 2-moment microphysics (hydrometeor mass and number concentration) and electrification and lightning to simulate a storm observed in Oklahoma during the TELEX-2004 experiment (Mansell et al. 2010, J. Atmos. Sci.). CCN concentration is predicted as a single category monodisperse size spectrum approximating small aerosols. Graupel and hail particle densities are also predicted and are mainly determined by rime density. Rime density in turn is a function of droplet size (affected by CCN concentration) and impact speed. Graupel density is also used as a crude roughness parameter to scale the drag coefficient in the fall speed.

A range of CCN concentrations (50 to 15000 cm-3) were tested in a weak CAPE (Convective Available Potential Energy) environment (918 J/kg) that produced weakly multicell convection. Greater CCN concentration has the expected effects of shifting the initial formation of rain drops via collision-coalescence to later times and higher altitudes. Even at the highest CCN concentrations, however, vapor supply in the updraft remains sufficient for droplets eventually to grow large enough for coalescence to become appreciable before the appearance of graupel, so the warm-rain process is not completely shut down in this case. Peak updraft values increased modestly with increasing CCN from 16.8 m/s (50 cm-3) to 19.5 m/s (500 cm-3). Above CCN of 500 cm-3, peak updraft varied little from 19.5 m/s.

Time-integrated mass of graupel increases monotonically with increasing CCN up to about 2000-3 and decreases somewhat at higher CCN concentrations (Fig. 1). Time-integrated updraft volume generally increases with greater CCN concentrations, as well, but reached a plateau for CCN greater than 500 cm-3. Other effects of CCN concentration were variable. The simulated storms had maximum flash rates of 0 to 17 per minute and from 0 to 150 total flashes (Fig. 1). The most intense electrification (total lightning sources) was for CCN concentrations of 1000 to 3000 cm-3, dropping off toward lower and higher CCN values (Fig. 1; no flashes at 50-100 cm-3, and 3-4 total flashes for CCN >= 8000 cm-3.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper180497.html.

Mansell, E. R., C. L. Ziegler, 2011: Aerosol (CCN) Effects on Simulated Storm Electrification and Precipitation. Preprints, 14th International Conference on Atmospheric Electricity, Rio de Janeiro, Brazil, International Commission on Atmospheric Electricity, CD-ROM, NA.

The effects of cloud condensation nuclei (CCN) concentrations strongly affected the microphysical and electrical evolution of a numerically simulated small storm. Graupel and lightning production increased monotonically as CCN increase from 50 cm-3 to about 2000 cm-3, where graupel production leveled off (up to 8000 cm-3 ). At higher CCN concentrations (>2000 cm-3 ), lightning activity either dropped dramatically (HM1) or remained steady (HM2), depending on the parameterization of Hallett-Mossop riming ice multiplication (HM1/HM2).

Marchand, R. N., N. Beagley, S. Thompson, T. P. Ackerman, D. M. Schultz, 2006: A bootstrap technique for testing the relationship between local-scale radar observations of cloud occurrence and large-scale atmospheric fields. Journal of the Atmospheric Sciences, 63, 2813-2830.

Mariani, Z., K. Strong, M. Wolff, P. Rowe, V. Walden, P. F. Fogal, T. Duck, G. Lesins, D. S. Turner, C. Cox, E. Eloranta, J. R. Drummond, C. Roy, D. D. Turner, D. Hudak, I. A. Lindenmaier, 2012: Infrared measurements in the Arctic using two Atmospheric Emitted Radiance Interferometers. Atmos. Meas. Tech., 5, 329-344.

The Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) is a moderate resolution (1 cm−1 ) Fourier transform infrared spectrometer for measuring the absolute downwelling infrared spectral radiance from the atmosphere between 400 and 3000 cm−1. The extended spectral range of the instrument permits monitoring of the 400–550 cm−1 (20–25 μm) region, where most of the infrared surface cooling currently occurs in the dry air of the Arctic. Spectra from the E-AERI have the potential to provide information about radiative balance, trace gases, and cloud properties in the Canadian high Arctic. Calibration, performance evaluation, and certification of the E-AERI were performed at the University of Wisconsin Space Science and Engineering Centre from September to October 2008. The instrument was then installed at the Polar Environment Atmospheric Research Laboratory (PEARL) Ridge Lab (610 m altitude) at Eureka, Nunavut, in October 2008, where it acquired one year of data. Measurements are taken every seven minutes year-round, including polar night when the solar-viewing spectrometers at PEARL are not operated.
A similar instrument, the University of Idaho’s Polar AERI (P-AERI), was installed at the Zero-altitude PEARL Auxiliary Laboratory (0PAL), 15 km away from the PEARL Ridge Lab, from March 2006 to June 2009. During the period of overlap, these two instruments provided calibrated radiance measurements from two altitudes. A fast line-by-line radiative transfer model is used to simulate the downwelling radiance at both altitudes; the largest differences (simulation- measurement) occur in spectral regions strongly influenced by atmospheric temperature and/or water vapour. The two AERI instruments at close proximity but located at two different altitudes are well-suited for investigating cloud forcing. As an example, it is shown that a thin, low ice cloud resulted in a 6% increase in irradiance. The presence of clouds creates a large surface radiative forcing in the Arctic, particularly in the 750–1200 cm−1 region where the downwelling radiance is several times greater than clear-sky radiances, which is significantly larger than in other more humid regions.

Marsh, P. T., J. S. Kain, V. Lakshmanan, A. J. Clark, N. M. Hitchens, J. Hardy, 2012: A Method for Calibrating Deterministic Forecasts of Rare Events. Weather and Forecasting, 27, 531-538.

Convection-allowing models offer forecasters unique insight into convective hazards relative to numerical models using parameterized convection. However, methods to best characterize the uncertainty of guidance derived from convection-allowing models are still unrefined. This paper proposes a method of deriving calibrated probabilistic forecasts of rare events from deterministic forecasts by fitting a parametric kernel density function to the model’s historical spatial error characteristics. This kernel density function is then applied to individual forecast fields to produce probabilistic forecasts.

Mazur, V., 2011: Physical processes during development of upward leaders from tall structures. Journal of Electrostatics, 69, 97-110.

McCarroll,, A., M. Yeary, D. Hougen, V. Lakshmanan, S. Smith, 2010: Approaches for Compression of Super-Resolution {WSR-88D} Data. {IEEE} Tran. on Geosc. and Remote Sensing Letters, PP, 191-195.

Available online at http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5546900&tag=1.

McFarquhar, G. M., S. Ghan, J. Verlinde, A. Korolev, J. W. Strapp, B. Schmid, J. Tomlinson, M. Wolde, S. Brooks, D. Cziczo, M. Dubey, J. Fan, C. Flynn, I. Gultepe, J. Hubbe, M. Gilles, A. Laskin, P. Lawson, W. R. Leaitch, P. Liu, X. Liu, D. Lubin, C. Mazzoleni, A. M. Macdonald, R. Moffet, H. Morrison, M. Ovtchinnikov, M. D. Shupe, D. D. Turner, S. Xie, A. Zelenyuk, K. Bae, M. Freer, A. Glen, 2011: Indirect and semi-direct aerosol campaign (ISDAC): The impact of Arctic aerosols on clouds. Bulletin of the American Meteorological Society, 92, 183-201.

A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the arctic boundary layer in the vicinity of Barrow, Alaska was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) sponsored by the Department of Energy Atmospheric Radiation Measurement (ARM) and Atmospheric Science Programs. The primary aim of ISDAC was to examine effects of aerosols on clouds that contain both liquid and ice water for clean and polluted environments. ISDAC utilized the ARM permanent observational facilities at Barrow. These include a cloud radar, a polarized micropulse lidar, and an atmospheric emitted radiance interferometer as well as instruments specially deployed for ISDAC measuring aerosol, ice fog, precipitation and spectral shortwave radiation. The National Research Council of Canada Convair-580 flew 27 sorties during ISDAC, collecting data using an unprecedented 42 state-of-the-art cloud and aerosol instruments for more than 100 hours on 12 different days. Data were obtained on a number of days, including above, below and within single- layer stratus on 8 April and 26 April 2008. These data enable a process-oriented understanding of how aerosols affect the microphysical and radiative properties of arctic clouds influenced by different surface conditions and aerosol loads. Observations acquired on a heavily polluted day, 19 April 2008, are enhancing this understanding. Data acquired in cirrus on transit flights between Fairbanks and Barrow are improving our understanding of the performance of cloud probes in ice. Ultimately the ISDAC data will be used to improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales and pollution regimes, and to determine the extent to which long-term surface-based measurements can provide retrievals of aerosols, clouds, precipitation and radiative heating in the Arctic.

McFarquhar, G. M., B. Schmid, A. Korolev, J. A. Ogren, P. B. Russell, J. Tomlinson, D. D. Turner, W. Wiscombe, 2011: Airborne Instrumentation Needs for Climate and Atmospheric Research (2011). Bulletin of the American Meteorological Society, 92, 1193-1196.

The Atmospheric Radiation Measurement (ARM) program hosted a workshop to bring together graduate students, postdoctoral fellows, and senior researchers working in atmospheric sciences at U.S. and foreign universities and government laboratories to discuss state-of-the-art techniques and necessary advances to realize effective airborne measurements of atmospheric parameters for climate and weather research.

McGovern, A., D. H. Rosendahl, A. Kruger, M. G. Beaton, R. A. Brown, K. K. Droegemeier, 2007: Understanding the formation of tornadoes through data mining. Extended Abstracts, 5th Conference on Artificial Intelligence and its Applications to Environmental Sciences, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 4.1.

McGovern, A., D. H. Rosendahl, R. A. Brown, K. K. Droegemeier, 2011: Identifying predictive multi-dimensional time series motifs: An application to severe weather prediction. Data Mining and Knowledge Discovery, 22, 232-258.

McLaughlin, D., D. Pepyne, B. Philips, J. Kurose, M. Zink, D. Westbrook, E. Lyons, E. Knapp, A. Hopf, A. Defonzo, R. Contreras, T. Djaferis, E. Insanic, S. Frasier, V. Chandrasekar, F. Junyent, N. Bharadwaj, Y. Wang, Y. Liu, B. Dolan, K. Droegemeier, J. Brotzge, M. Xue, K. Kloesel, K. Brewster, F. Carr, S. Cruz-Pol, K. Hondl, P. Kollias, 2009: Short-Wavelength Technology and the Potential For Distributed Networks of Small Radar Systems. Bulletin of the American Meteorological Society, 90, 1797-1817.

Dense networks of short-range radars capable of mapping storms and detecting atmospheric hazards are described. Composed of small X-band (9.4 GHz) radars spaced tens of kilometers apart, these networks defeat the Earth curvature blockage that limits today's long-range weather radars and enables observing capabilities fundamentally beyond the operational state-of-the-art radars. These capabilities include multiple Doppler observations for mapping horizontal wind vectors, subkilometer spatial resolution, and rapid-update (tens of seconds) observations extending from the boundary layer up to the tops of storms. The small physical size and low-power design of these radars permits the consideration of commercial electronic manufacturing approaches and radar installation on rooftops, communications towers, and other infrastructure elements, leading to cost-effective network deployments. The networks can be architected in such a way that the sampling strategy dynamically responds to changing weather to simultaneously accommodate the data needs of multiple types of end users. Such networks have the potential to supplement, or replace, the physically large long-range civil infrastructure radars in use today.

Melnikov, V. M., D. S. Zrnic, 2005: Measurements of polarimetric parameters at low signal-to-noise ratios. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P9R.2.

Melnikov, A. V., V. M. Melnikov, A. V. Ryzhkov, 2005: On the differential phase in the melting layer. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P9R.9.

Melnikov, V. M., 2006: One-lag estimators for cross-polarization measurements. Journal of Atmospheric and Oceanic Technology, 23, 915-926.

Estimators of the linear depolarization ratio (LDR) and cross-polarization correlation coefficients (ρxh ) free from noise biases are devised. The estimators are based on the 1-lag correlation functions. The 1-lag estimators can be implemented with radar with simultaneous reception of copolar and cross-polar returns. Absence of noise biases makes the1-lag estimators useful in eliminating variations of the system gain and in observations of heavy precipitation with enhanced thermal radiation. The 1-lag estimators allow for measurements at lower signal-to-noise ratios than the conventional algorithms.

The statistical biases and standard deviations of 1-lag estimates are obtained via the perturbation analysis. It is found that both the 1-lag and conventional estimates of ρxh experience strong statistical biases at ρxh less than 0.3 (i.e. at low canting angles of oblate hydrometeors) and a procedure to correct for this bias is proposed.

Melnikov, V. M., D. S. Zrnic, 2007: Autocorrelation and cross-correlation estimators of polarimetric variables. Journal of Atmospheric and Oceanic Technology, 24, 1337-1350.

Herein are proposed novel estimators of differential reflectivity, ZDR, and correlation coefficient, ρ, between horizontally and vertically polarized echoes. The estimators use autocorrelations and cross-correlations of the returned signals to avoid bias by omnipresent but varying white noise. These estimators are considered for implementation on the future polarimetric WSR-88D network. On the current network the reflectivity factor is measured at signal-to-noise ratios (SNR) as low as 2 dB and the same threshold is expected to hold for the polarimetric variables. At such low SNR and all the way up to SNR = 15 dB, the conventional estimators of differential reflectivity and the copolar correlation coefficient are prone to errors due to uncertainties in noise levels caused by instability of radar devices, thermal radiations of precipitation and the ground, and wideband radiation of electrically active clouds. Noise variations less than 15 dB can bias the estimates beyond apparatus accuracy. For short we refer to the estimators of ZDR and ρ free from noise bias as the “1-lag estimators” because these are derived from 1-lag correlations. The estimators are quite robust and the only weak assumption for validity is that spectral widths of signals from vertically and horizontally polarized returns are equal. This assumption is verified on radar data. Radar observations demonstrate the validity of these estimator and lower sensitivity to interference signals than the conventional algorithms.

Melnikov, V. M., D. S. Zrnic, R. J. Doviak, Y. L. Kogan, P. B. Chilson, D. B. Mechem, 2007: The WSR-88D observes non precipitating clouds. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P6A3.

Preliminary observations made with the WSR-88D show sufficient sensitivity of the radar to measure parameters of non-precipitating clouds. Cloud characteristics can be obtained with the WSR-88D in scanning mode, i.e., to generate “instant” fields of spectral moments. Cloud observations with the WSR-88Ds can be used in studies related to the development and evolution of clouds and precipitation, cloud model parameterization, application to climate effects, and radiation transfer in the atmosphere

Melnikov, V., D. S. Zrnic, R. M. Rabin, P. Zhang, 2008: Radar polarimetric signatures of fire plumes in Oklahoma. Geophysical Research Letters, 35, .

Radar observations of wild fire plumes in Oklahoma carried out with the prototype of dual polarization S-band WSR-88D weather radar are presented. The observations show that the copolar correlation coefficients between horizontally and vertically polarized returns in the plumes are mostly less than 0.4 and this can be used in identification of plumes.

Melnikov, V., R. J. Doviak, 2008: Strong wind shears in stratiform precipitation observed with weather radar. Extended Abstracts, 13th Conference on Aviation, Range, and Aerospace Meteorology., New Orleans, LA, USA, AMS, 12.4.

Melnikov, V. M., R. J. Doviak, 2009: Turbulence and wind shears in layers of large Doppler spectrum width in stratiform precipitation. Journal of Atmospheric and Oceanic Technology, 26, 430-443.

Weather radar observations of stratiform precipitation often reveal regions having very large measured Doppler spectrum widths, exceeding 7 and sometimes 10 m/s. These widths are larger than those typically found in thunderstorms; widths larger than 4 m/s are associated with moderate or severe turbulence in thunderstorms. We have found that stratiform precipitation has layers of widths larger than 4 m/s in more than 80% of cases studied, wherein shear of wind on scales large compared to the dimensions of radar resolution volume is the dominant contributor to spectrum width. Analyzed data show that if width ≤ 7 m/s, and if the layers are not wavy or patchy, these layers have weak turbulence. On the other hand, regions having widths > 4 m/s in patches or in wave-like structures are likely to have moderate to severe turbulence with the potential to be a hazard to safe flight. To separate contributions to spectrum width from wind shear and turbulence, and to evaluate the errors in turbulence estimates, data have been collected with elevation increments much less than a beamwidth. Despite beamwidth limitations, the small elevation increments reveal impressive structures in the fields. For example, the “cat’s eye” structure associated with Kelvin-Helmholtz waves is clearly observed in the fields of spectrum width but not in the reflectivity or velocity fields.

Melnikov, V. M., D. S. Zrnic, R. M. Rabin, R. B. Pierce, P. Zhang, 2009: Radar polarimetric signatures of fire plumes. Extended Abstracts, 25th Conference on International Interactive Information and Processing Systems (IIPS), Phoenix, AZ, USA, AMS, 15.2.

Available online at http://ams.confex.com/ams/89annual/techprogram/paper_144620.htm.

Melnikov, V. M., D. B. Mechem, P. B. Chilson, R. J. Doviak, D. S. Zrnic, Y. L. Kogan, 2009: Prospects of Cloud Volume Imaging with the WSR-88D Radar. Proc. 19th Annual ARM Science Team Meeting, Louisville, KY, USA, DOE, 78-78.

Available online at http://www.arm.gov/publications/proceedings/conf19/index.php.

Melnikov, V. M., D. S. Zrnic, R. M. Rabin, 2009: Polarimetric radar properties of smoke plumes: A model.. Journal of Geophysical Research - D: Atmospheres, 114, .

Smoke plumes can be recognized with the polarimetric WSR-88D weather radar using low correlation coefficient between signals in the horizontal and vertical channels. A model that describes radar measurements at 10-cm wavelength is developed. Using the model it is concluded that smoke scatterers have a needle-like form. The scatterers flutter with the mean angle of 23-27 deg which is the angle between the major particle's axis and horizontal plane. It is inferred that the scatterers have the major-to-minor axis ratio larger than 6.

Melnikov, V., P. B. Chilson, D. B. Mechem, 2009: Extending the capabilities of the polarimetric WSR-88D: observations of cirrus clouds and moist layers. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, P3.1.

http://ams.confex.com/ams/34Radar/techprogram/paper_155817.htm

Melnikov, V., T. J. Schuur, A. V. Ryzhkov, 2009: Recognition of lightning echoes with the polarimetric WSR-88D. Extended Abstracts, 34th Conference on Radar Metorology, Williamsburg, VA, USA, AMS, P13.8.

http://ams.confex.com/ams/34Radar/techprogram/paper_155320.htm

Melnikov, V., D. S. Zrnic, A. V. Ryzhkov, A. Zahrai, J. K. Carter, 2009: Validation of attenuation correction at X band performed with collocated S-band polarimetric radar. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, 11A.5.

http://ams.confex.com/ams/34Radar/techprogram/paper_155322.htm

Melnikov, V., R. R. Lee, N. J. Langlieb, 2010: Hail reflectivity signatures from two adjacent WSR-88Ds: carrier frequency and calibration issues. Extended Abstracts, 26th Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, AMS, CD-ROM, 8.5.

Available online at http://ams.confex.com/ams/90annual/techprogram/paper_161721.htm.

Melnikov, V., R. Lee, N. Langlieb, 2010: Resonance scattering at close wavelengths in hail and “clear air”. Extended Abstracts, European Conference on Radar Meteorology, ERAD-2010, Sibiu, Romania, Romanian Weather Service, 1.7.

Melnikov, V., M. Leskonen, J. Koinstinen, 2010: Spectral polarimetric parameters of radar signals from atmospheric biota.. Preprints, European Conference on Radar Meteorology, ERAD-2010, Sibiu, Romania, Romanian Weather Service, 14.3.

Melnikov, V. M., D. S. Zrnic, R. J. Doviak, P. B. Chilson, D. B. Mechem, Y. L. Kogan, 2011: Prospects of the WSR-88D Radar for Cloud Studies. Journal of Applied Meteorology and Climatology, 50, 859-872.

Sounding of clouds with the 10-cm wavelength Weather Surveillance Radar-1988 Doppler (WSR-88D) is discussed. Enhancements to signal processing and volume coverage patterns of the WSR-88D allow observations of a variety of clouds with reflectivities as low as −25 dBZ (at a range of 10 km). The high sensitivity of the WSR-88D, its wide velocity and unambiguous range intervals, and the absence of attenuation allow accurate measurements of the reflectivity factor, Doppler velocity, and spectrum width fields in clouds to ranges of about 50 km. Fields of polarimetric variables in clouds, observed with a research polarimetric WSR-88D, demonstrate an abundance of information and help to resolve Bragg and particulate scatter. The scanning, Doppler, and polarimetric capabilities of the WSR-88D allow real-time, three-dimensional mapping of cloud processes, such as transformations of hydrometeors between liquid and ice phases. Pockets of high differential reflectivities are frequently observed in clouds; maximal values of differential reflectivity exceed 8 dB, far above the level observed in rain. The establishment of the WSR-88D network consisting of 157 polarimetric radars can be used to collect cloud data at any radar site, making the network a potentially powerful tool for climatic studies.

Available online at http://journals.ametsoc.org/doi/abs/10.1175/2010JAMC2303.1.

Melnikov, V., M. Yeary, R. Huck, R. Kelley, 2011: Potentials of frequency agile Ka and W band cloud radars. Extended Abstracts, 2011 IEEE Rarar Conference, RADCON11, Cansas City, MO, USA, IEEE, 3146.

Melnikov, V., R. J. Doviak, D. S. Zrnic, D. J. Stensrud, 2011: Mapping Bragg Scatter with a Polarimetric WSR-88D. Journal of Atmospheric and Oceanic Technology, 28, 1273-1285.

Using a polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) radar to distinguish Bragg scatterers from insects and birds in an optically clear atmosphere has the potential to provide information on convective boundary layer depth. Measured median differential reflectivities ZDR of Bragg scatterers lie between −0.08 and 0.06 dB, which supports the hypothesis that the intrinsic ZDR of Bragg scatters is 0 dB. Thus, the intrinsic 0 dB of Bragg scatter can be used for verifying of ZDR radar calibration. If insects and birds are spatially separated from Bragg scatterers, the dual-polarization capability of the WSR-88D allows distinguishing echoes from these two types of scatterers since ZDR from biota is significantly larger than 0 dB. In mixtures of Bragg and biota scatter, polarimetric spectral analysis shows differences in portions of the H and V spectra where birds and insects could be contaminating echoes from Bragg scatterers. Enhancements to data collection and signal processing allow power measurement, with a standard deviation of about 1 dB, of weak echoes from Bragg scatterers having equivalent reflectivity factors of about −28 dBZ at distance of 10 km from the radar. This level of reflectivity corresponds to a refractive index structure parameter of about 4 × 10^(−15) m^(−2/3), a typical magnitude found in maritime air.

Melnikov, V., P. T. Schlatter, 2011: Enhancing sensitivity on the polarimetric WSR-88D. Extended Abstracts, 27th Conference on Interactive Information and Processing Systems (IIPS), Seattle, WA, USA, AMS, 14.3.

2D despeckling algorithm to compansate for the 3-dB loss in the dual polarization WSR-88Ds.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper178856.html.

Melnikov, V., R. J. Doviak, D. S. Zrnic, D. J. Stensrud, 2011: Fine structures of refractivity in the boundary layer revealed with a polarimetric WSR-88D. Extended Abstracts, 35-th Conference on Radar Meteorology, Pittsburgh, PA, USA, AMS, 191078.

Types of radar Bragg scatter in clear air.

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper191078.html.

Melnikov, V., 2011: Polarimetric Properties of Ice Cloud Particles at S band. Preprints, 35-th Conference on Radar Meteorology, Pittsburgh, PA, USA, AMS, 191041.

High ZDR in clouds observed with the WSR-88D.

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper191041.html.

Melnikov, V., M. Yeary, R. Huck, R. Kelley, J. Phillips, 2011: Potentials of frequency agile Ka and W band cloud radars. Extended Abstracts, 35-th Conference on Radar Meteorology, Pittsburgh, PA, USA, AMS, 5A.4.

Frequency agile radars in meteorology

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper191562.html.

Melnikov, V., R. Lee, N. Langlieb, 2012: Resonance Effects within S Band in Echoes from Birds. IEEE Geoscience and Remote Sensing Letters, 9, 413-416.

It is shown that the scattering resonance effects in echoes from migrating birds are so strong that a 10% frequency deviation within S band can result in more than 10 dB changes in reflectivity values. Differential reflectivity values from adjacent polarimetric WSR-88D weather radars operating at offset frequencies can differ by several dB in “clear air” echoes.

Michaud, D., R. Palmer, D. Bodine, P. Heinselman, B. Cheong, 2009: A new clutter censoring technique - Updates on radar refractivity retrieval. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P10.21.

Michaud, D. S., R. D. Palmer, D. Bodine, P. L. Heinselman, B. L. Cheong, 2010: Updates on radar refractivity retrieval – Quality control improvements and 2009 field experiment to determine causes of bias. Preprints, 26th Conf. Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., 11B.5.

Over the last year, radar-derived refractivity has been continuously estimated at the University of Oklahoma using two Oklahoma WSR-88D radars (KTLX, KFDR). Refractivity is calculated using phase measurements derived from stationary clutter targets in the radar's domain, which is typically limited to 40-60 km due to earth curvature. Previous work has shown the utility of short-term refractivity changes as a proxy for low-level moisture perturbations. These may in turn be used as a predictor for focal points of convection initiation.

Unfortunately using current quality control (QC) methods, the domain used for refractivity can contain clutter points with poor phase coherency, which should be removed before being used in the algorithm. The algorithm interpolates and spatially filters the data due to the inherent statistically uncertainty and the general sparseness of the phase measurements, resulting in a spatial resolution of approximately 4 km. If clutter points with questionable phase data are allowed to pass through the algorithm, surrounding data points (up to a distance of 4 km) may be impacted, especially in regions with a low number of clutter points. Consequently, estimates of phase and refractivity will have degraded quality. This occurs most frequently near the edge of the clutter domain or where clutter signals may be dominated by tress. It can be shown that the existing algorithm had deteriorated refractivity quality when used on windy days, when these clutter targets were moving irregularly and introducing error-prone phase data into the algorithm. By determining which targets move in these situations using their spectral characteristics and phase coherency, we can censor these points and improve estimates of the refractivity field. An extensive statistical study will be presented using the Oklahoma Mesonet data as ground truth. In addition, an improved phase QC methodology will be proposed, which significantly improves the ultimate quality of the refractivity data.

During the course of this project a diurnal refractivity bias between Mesonet surface observations and the radar has been observed. This bias tends to peak around 00 UTC, and is most prevalent in the summertime. The observations of this bias has led to a field experiment aimed at answering the underlying cause. The experiment includes a modified Mesonet station, which can monitor refractivity at 1.5 and 9 meters at one-minute intervals, as well as vertical profiles provided by an unmanned aerial vehicle (UAV) outfitted with a full array of meteorological sensors. The Mesonet tower provides insight as to the near-surface refractivity gradient during periods of bias, and whether or not it may be due to changes in sampling height as a side effect of beam propagation changes. The UAV provides a refractivity profile over a deep layer, and can sample the evolution of the changing profile in accompaniment to Mesonet data during periods of bias. Profiles of refractivity for periods of bias using both data sources, as well as an analysis of correlation with the intensity and duration of observed bias, will be presented.

Miller, M. L., V. Lakshmanan, T. M. Smith, 2012: Developing Quality Control Techniques for a CONUS-Wide Multi-Year Radar-Derived Rotation Track Climatology. Preprints, 28th Conference on IIPS, New Orleans, LA, USA, AMS, 7B.7.

The Multi-Year Reanalysis Of Remotely-Sensed Storms (MYRORSS) project is a cooperative effort between the National Oceanic and Atmospheric Administration's (NOAA) National Severe Storms Laboratory (NSSL) and the National Climatic Data Center (NCDC) to reconstruct and evaluate numerical model output and radar products derived from 16 years of WSR-88D data over the CONUS. Several years of a hail climatology using the Maximum Estimated Size of Hail (MESH) parameter have already been processed and a rotation track climatology is nearly ready to begin processing.

The rotation track fields are created by using the local, linear, least squares derivative (LLSD) algorithm to produce the azimuthal shear field (Smith and Elmore 2004). After performing quality-control on the reflectivity field and stamping out azimuthal shear areas not associated with at least 40 dBZ, an azimuthal shear range-correction is applied. Data from multiple radars are then merged together to form two-dimensional low-level (0-3 km) and mid-level (3-6 km) maximum azimuthal shear fields. These maximum azimuthal shear fields are accumulated over time to create rotation tracks.

Due to the inherent noisiness of velocity-derived fields, a great deal of quality control is needed before process the rotation track climatology. Even small non-meteorological contaminants can become large problems when accumulated over time. To quality control the azimuthal shear fields, the wind field from a 20-km Rapid Update Cycle model (RUC) point sounding at each radar site is used as a first guess for the WSR-88D velocity dealiasing algorithm. Clusters of shear in the maximum azimuthal shear fields then are isolated using hysteresis segmentation. Multiple Hypothesis Tracking (MHT) techniques are then used to identify and associate these segments throughout time. A cost function based on size difference, segment proximity, and other factors is used to determine the ranked k-best associations. The associations with the lowest cost functions are then made and unassociated segments, usually non-meteorological contaminants, are pruned.

Applications of these quality control techniques and preliminary rotation track climatology results will be discussed.

Available online at http://ams.confex.com/ams/92Annual/webprogram/Paper195555.html.

Monroe, K., D. A. Morris, D. S. LaDue, V. Holtz, H. Moser, E. M. Quoetone, P. T. Schlatter, J. G. LaDue, B. Rooks, S. Van Cooten, J. Kelley, R. Fowler, M. Stallings, J. A. Smith, C. Spannagle, 2011: Role Playing Scenario of a Landfalling Tropical System. Preprints, Tropical Cyclones: Engaging and Educating The Public- More Effectively Communicating the Science of Tropical Climate and Tropical Cyclones, Seattle, WA, USA, American Meteorological Society, 1.3.

The NWS Warning Decision Training Branch, in collaboration with an interdisciplinary team comprised of NWS forecasters, broadcast media, emergency managers, Sea Grant personnel, and FEMA Hurricane Program Management, facilitated a simulation of NWS products and services as they occur prior to, during, and after landfall of a tropical system in North Carolina. Particular emphasis was placed on the hydrologic aspects of Tropical Storm Ernesto in 2006. To have a level playing field and be guided by subject matter experts, participants played a role outside of their areas of expertise, functioning as members of the Integrated Warning Team (NWS forecasters, emergency managers, and broadcast media). The scenario design allowed participants to learn the importance of improved shared situation awareness and improved communications during tropical events. An overview of the scenario and its objectives, distance learning modules under development, and lessons learned are presented.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper183882.html.

Morris, M., P. Chilson, G. Zhang, Q. Cao, R. Palmer, M. Teshiba, L. Kanofsky, T. Schuur, A. Ryzhkov, 2008: Validation of rainddrop size distributions retrieved from polarimetric radar variables. Preprints, Symposium on Recent Developments in Atmospheric Applications of Radar and Lidar, New Orleans, LA, USA, American Meteorological Society, P2.4.

Morris, M., P. Chilson, A. Ryzhkov, T. Schuur, M. Teshiba, R. Palmer, 2008: Application of polarimateric radar to improve wind profiler-based microphysical retrieval. Preprints, Fifth European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Finnish Meteorological Institute, 7.4.

Morris, M. P., P. B. Chilson, T. J. Schuur, A. V. Ryzhkov, 2009: Microphysical retrievals from simultaneous polarimetric and profiling radar observations.. Annales Geophysicae, 27, 4435-4448.

Nai, F., R. Palmer, S. Torres, 2010: Wind turbine clutter mitigation using non-stationary signal processing methods. Preprints, 6th European Conf. on Radar in Meteorology and Hydrology: Adv. in Radar Technology, Sibiu, Romania, National Meteorological Administration, Romania, 3.2.

Nai, F., S. Torres, R. Palmer, 2011: Mitigation of wind-turbine clutter using range-Doppler spectral analysis. Extended Abstracts, 35th Conf. on Radar Meteor., Pittsburgh, PA, USA, Amer. Meteor. Soc., CD-ROM, 164.

Wind turbines produce contaminating returns that can bias estimates of the spectral moments and polarimetric variables of weather signals. These biases can propagate to and negatively influence the output of automatic algorithms, such as severe weather detection and quantitative precipitation estimates. Moreover, existing ground clutter filters are ineffective at removing wind turbine clutter (WTC) contamination because the moving components of wind turbines produce clutter signals spanning a wide range of nonzero Doppler velocities. Hence, it is important to devise signal processing techniques that mitigate this special type of contamination so that weather signals can be recovered and used to estimate meaningful meteorological variables. The problem is particularly challenging because WTC signals are inherently non-stationary due to the moving wind turbine blades; thus, traditional time-domain or frequency-domain clutter-mitigation methods are ineffective. In this work, we propose a range-Doppler spectral processing technique to mitigate WTC contamination that is compatible with typical weather radar modes of operation. The proposed technique successfully exploits both spectral and spatial differences between WTC and weather signals. Following an algorithm description, simulations and real data are used to test the effectiveness of this novel WTC mitigation scheme.

Nai, F., R. Palmer, S. Torres, 2011: Wind turbine clutter mitigation using range-Doppler domain signal processing method. Extended Abstracts, 27th Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Seattle, WA, USA, Amer. Meteor. Soc., CD-ROM, 9.4.

Wind turbines produce clutter signals that can bias estimates of the spectral moments and polarimetric variables of weather signals. These biases can propagate to and negatively influence the output of automatic algorithms, such as severe weather detection and quantitative precipitation estimates. Moreover, existing ground clutter filters are ineffective at removing wind turbine clutter (WTC) contamination because the moving components of the wind turbine produce clutter signals with non-zero Doppler frequency shifts. As the first step in any mitigation scheme, an automatic WTC detection algorithm is necessary and was recently developed by University of Oklahoma and National Severe Storm Laboratory scientists. The detection algorithm operates on a gate-by-gate basis and uses temporal and spectral features to flag contaminated data. After successfully detecting the presence of WTC, the goal is to devise signal processing algorithms that mitigate this contamination so that the weather signal can be recovered and used to estimate the spectral moments and polarimetric variables. However, WTC is inherently non-stationary due to the moving wind turbine blades, which makes frequency-domain-filtering based clutter mitigation methods ineffective. In this work, we propose a new signal processing technique to separate the WTC from the weather signal in the range-Doppler domain. This technique exploits the different spatial and spectral characteristics of WTC and weather signals. Real weather signals and WTC data are used to test the effectiveness of the mitigation scheme.

Nallapareddy, A., A. Shapiro, J. Gourley, 2011: A climatology of nocturnal warming events associated with cold-frontal passages in Oklahoma. Journal of Applied Meteorology and Climatology, 50, 2042-2061.

A sudden increase in temperature during the nighttime hours accompanies the passages of some cold fronts. In some cold front–associated warming events, the temperature can rise by as much as 10°C and can last from a few minutes to several hours. Previous studies suggest that these events are due to the downward transport of warmer air by the strong and gusty winds associated with the cold-frontal passages. In this study, a climatology of nocturnal warming events associated with cold fronts was created using 6 yr of Oklahoma Mesonetwork (Mesonet) data from 2003 to 2008. Nocturnal warming events associated with cold-frontal passages occurred surprisingly frequently across Oklahoma. Of the cold fronts observed in this study, 91.5% produced at least one warming event at an Oklahoma Mesonet station. The winter months accounted for the most events (37.9%), and the summer months accounted for the fewest (3.8%). When normalized by the monthly number of cold-frontal passages, the winter months still had the most number of warming events. The number of warming events increased rapidly from 2300 to 0200 UTC; thereafter, the number of events gradually decreased. A spatial analysis revealed that the frequency of warming events decreased markedly from west to east across the state. In contrast, the average magnitude of the warming increased from west to east. In contrast to control periods (associated with cold-frontal passages without nocturnal warming events), warming events were associated with weaker initial winds and stronger initial temperature inversions. Moreover, the nocturnal temperature inversion weakened more during warming events than during control periods and the surface wind speeds increased more during warming events than during control periods. These results are consistent with previous studies that suggest the warming events are due to the “mixing out” of the nocturnal temperature inversion.

Newman, J. F., D. S. LaDue, P. L. Heinselman, 2008: Identifying critical strengths and limitations of current radar systems. Preprints, 25th Conference on Severe Local Storms, Savannah, GA, USA, American Meteorological Society, 7B.5.

Current weather radars are nearing the end of their expected 20-year engineering design lifetime. One replacement system currently under consideration is multifunction phased array radar (MPAR). The purpose of this study is to illustrate the critical strengths and weaknesses of current radar systems to decision-makers and to determine the suitability of MPAR to users' needs. The study focuses on two key stakeholder groups: National Weather Service (NWS) forecasters and broadcast meteorologists. Interviews are conducted with a variety of radar users from these groups, including Science and Operations Officers (SOOs), Warning Coordination Meteorologists (WCMs), and chief broadcast meteorologists. During the interview, participants are asked to tell stories which exemplify the critical strengths and limitations of current radar technology. Nine interviews have been conducted to date: five with NWS forecasters and four with broadcast meteorologists.

Preliminary findings indicate that the roles of broadcast meteorologists differ widely from those of NWS forecasters. Broadcast meteorologists use radar to anticipate warnings issued by NWS and to make decisions about cutting into regular programming to provide severe weather coverage. These decisions have the potential to impact the television station financially and to aggravate viewers. In addition, broadcast meteorologists use radar on the air to illustrate the current threat to viewers. NWS forecasters use radar data to make important decisions about issuing warnings and face different concerns from those of broadcast meteorologists. Participants from both groups have stressed the importance of frequent scans at the lowest elevation angle, particularly for tornado detection; some have even admitted to re-starting the volume scan to obtain this information. Other common themes in the interviews include radar horizon issues, de-aliasing problems, beam spreading, and detection of precipitation type.

Available online at http://ams.confex.com/ams/pdfpapers/142180.pdf.

Newman, J. F., D. S. LaDue, P. L. Heinselman, 2009: 25th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology. Preprints, 25th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Williamsburg, VA, USA, Amer. Meteor. Soc., 11B.4.

Newman, J. F., V. Lakshmanan, P. L. Heinselman, T. M. Smith, 2011: Range correction for radar-derived azimuthal shear: applications to a tornado detection algorithm. Extended Abstracts, 27th Conference on Interactive Information Processing Systems (IIPS), Seattle, WA, USA, AMS, 8B.4.

The current Tornado Detection Algorithm (TDA) used with the Weather Surveillance Radar- 1988 Doppler network utilizes an input velocity field that is often noisy and subject to de-aliasing errors. The current TDA also relies on azimuthal shear calculations, which are affected by noisy velocity data and can degrade significantly with range. Because of these and other data accuracy issues, the current TDA is prone to producing false detections and inaccurate circulation tracks.

Coincident with the advent of new radar-derived products and ongoing research involving new weather radar systems (e.g., Phased Array Radar), the National Severe Storms Laboratory is developing an improved TDA. A primary component of this algorithm will be the local, linear least squares derivatives (LLSD) azimuthal shear field. The LLSD method uses rotational derivatives of the velocity field and is less affected by noisy velocity data in comparison to the more traditional “peak-to-peak” azimuthal shear calculations.

Initial detections will be made on a field of maximum low-level LLSD shear and diagnosed for potentially tornadic characteristics. Although LLSD shear is less range-dependent than peak-to-peak shear, some range dependency is unavoidable. A preliminary study of 31 tornadoes indicated that the threshold LLSD shear value needed to detect tornadoes was moderately dependent on range from the radar. A regression analysis was completed to determine the relationship between range and shear values such that range-corrected shear values could be estimated.

Predictors in the regression equation include circulation diameter and calculated LLSD shear. The circulation diameter was estimated by calculating the distance between minimum and maximum velocity values at a constant range. This value is assumed to represent the diameter of a mesocyclone-scale circulation, with the understanding that small-scale circulations will not be resolvable at far ranges. The resulting regression equation was applied to range-degraded shear values from tornadic circulations in the initial test set. Range-corrected shear values were compared to actual tornado intensities, as determined by damage surveys, to assess their validity.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper184514.html.

Newman, J. F., V. Lakshmanan, P. L. Heinselman, T. M. Smith, 2011: Effects of radar range and azimuthal resolution on tornadic shear signatures: applications to a tornado detection algorithm. Extended Abstracts, 25th Conference on Severe Local Storms, Denver, CO, USA, AMS, P5.4.

The current Tornado Detection Algorithm (TDA) used with the Weather Surveillance Radar-1988 Doppler (WSR-88D) network utilizes an input velocity field that is often noisy and subject to de-aliasing errors. The current TDA also depends on azimuthal shear calculations, which are affected by noisy velocity data and can degrade significantly with range. Because of these and other data accuracy issues, the current TDA is prone to producing false detections and inaccurate circulation tracks.

Coincident with the advent of new radar-derived products and ongoing research involving new weather radar systems (e.g., Phased Array Radar; PAR), the National Severe Storms Laboratory is developing an improved TDA. A primary component of this algorithm will be the local, linear least squares derivatives (LLSD) azimuthal shear field. The LLSD method uses rotational derivatives of the velocity field and is less affected by noisy velocity data in comparison to the more traditional “peak-to-peak” azimuthal shear calculations.

Initial detections will be made on a field of maximum low-level LLSD shear and diagnosed for potentially tornadic characteristics. Although LLSD shear is less range-dependent than peak-to-peak shear, some range dependency is unavoidable. A preliminary study of 31 tornadoes indicated that the threshold LLSD shear value needed to detect tornadoes was moderately dependent on range from the radar. A regression analysis was completed to determine the relationship between range and shear values so that range-corrected shear values could be estimated.

In addition to range, azimuthal sampling is an important consideration in tornado detection. Of particular interest for this work is the azimuthal resolution of the National Weather Radar Testbed PAR in Norman, Oklahoma. The beamwidth of the PAR increases smoothly with increasing angle from boresight, ranging from 1.5° at boresight to 2.1° at an angle of 45° from boresight. Although overlapped sampling is applied to the PAR to increase the azimuthal resolution, the PAR does not currently reach the super-resolution capabilities in use with the WSR-88D network. A two -dimensional Rankine vortex model was used to demonstrate the effects of azimuthal resolution and range on peak-to-peak and LLSD shear calculations. Simulated Rankine vortices were sampled with azimuthal resolution mimicking that of the PAR and a typical WSR-88D radar and results were compared.

Available online at http://ams.confex.com/ams/25SLS/techprogram/paper_175382.htm.

Newman, J. F., P. L. Heinselman, 2011: Evolution of a quasi-linear convective system observed by phased-array radar. Extended Abstracts, 27th Conference on Interactive Information Processing Systems, Seattle, WA, USA, Amer. Meteor. Soc., 13B.5.

On 2 April 2010, a quasi-linear convective system (QLCS) formed in southwestern Oklahoma and northern Texas and moved eastward through central Oklahoma during the early morning hours. Storm formation was initially limited to the Oklahoma panhandle and southern Kansas, where an advancing cold front merged with a retreating dry line in an uncapped environment. An upper-level trough approached from the west overnight, supporting large-scale ascent and a strengthening southwesterly low-level jet. Soundings in central and northern Oklahoma on the evening prior to the event indicated a strongly capped environment with a deep elevated mixed layer. The arrival of the upper-level trough during the early morning hours of 2 April 2010 provided the ascent necessary to overcome convective inhibition and promote storm formation.

Marginally severe hail was reported with the earlier storms in southern Kansas, but the most severe damage resulted from the QLCS in southwestern Oklahoma. After the QLCS formed in southwestern Oklahoma, it moved eastward into a corridor of moderately high instability, with mixed-layer CAPE values exceeding 1000 J kg-1. Strong unidirectional low-level wind shear was supportive of organized bow echo structures and low-level mesovortices. Wind damage in Rush Springs, Oklahoma approached EF1-scale intensity and was likely associated with one of the mesovortices that formed along the leading edge of the QLCS.

The evolution of the QLCS was captured by the National Weather Radar Testbed Phased Array Radar (NWRT PAR) in Norman, Oklahoma. The NWRT PAR is an S-band radar with an electronically steered beam, allowing for rapid volumetric updates (~1 min) and user-defined scanning strategies. The rapid temporal updates and dense vertical sampling of the PAR created a detailed depiction of the evolution and damaging wind mechanisms associated with the QLCS. Features in the PAR data include microbursts, multicellular storm evolution, an intensifying rear-inflow jet, and a bowing segment and rotation associated with the Rush Springs damage. PAR data are analyzed and compared to data from the nearby S-band WSR-88D radar in Twin Lakes, Oklahoma and C-band Terminal Doppler Weather Radar in Oklahoma City, Oklahoma.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper184493.html.

Orescanin, M. B., T. Y. Yu, C. D. Curtis, D. S. Zrnic, D. E. Forsyth, 2005: Signal processing of Beam-multiplexed data for Phased-Array weather radar. Extended Abstracts, 32nd Conference on Radar Meteorology, Alburqueue, NM, USA, American Meteorological Society, CD-ROM, 4R.6.

The S-band Phased Array Radar(PAR) has been recently installed at the National Weather Radar Testbed (NWRT) in Norman, Oklahoma. It is equipped with the SPY-1A phased array antenna loaned by the NAVY and can rapidly and adaptively scan multiple regions of interest. Beam-multiplexing makes further use of the PAR's beam agility to provide high-quality and rapid-update weather observations. In a beam-multiplexing mode regions of interest are re-sampled after weather signals become uncorrelated. As a result, the statistical error of spectral moment estimation can be reduced optimally through the average of a number of independent measurements. Moreover, PAR can be tasked to probe other regions during the period of re-sampling to maximize the use of radar resources. Thus PAR can provide fast update of weather information in regions of interest. In this work, the idea of beam-multiplexing is presented and verified using numerical simulation. An experiment was designed to demonstrate the feasibility and advantage of beam-multiplexing. The PAR and the research WSR-88D (KOUN) were coordinated to simultaneously scan the same region using beam-multiplexing and conventional sampling, respectively. Preliminary results have shown that data quality and update rate can be improved using PAR beam-multiplexing.

Ortega, K. L., T. M. Smith, K. L. Manross, K. A. Scharfenberg, A. Witt, A. G. Kolodziej, J. J. Gourley, 2009: The severe hazards analysis and verification experiment. Bulletin of the American Meteorological Society, 90, 1519-1530.

During the springs and summers of 2006 through 2008, scientists from the National Severe Storms Laboratory and students from the University of Oklahoma have conducted an enhanced severe-storm verification effort. The primary goal for the Severe Hazards Analysis and Verification Experiment (SHAVE) was the remote collection of high spatial and temporal resolution hail, wind (or wind damage), and flash-flooding reports from severe thunderstorms. This dataset has a much higher temporal and spatial resolution than the traditional storm reports collected by the National Weather Service and published in Storm Data (tens of square kilometers and 1–5 min versus thousands of square kilometers and 30–60 min) and also includes reports of nonsevere storms that are not included in Storm Data. The high resolution of the dataset makes it useful for validating high-resolution, gridded warning guidance applications.

SHAVE is unique not only for the type of data collected and the resolution of that data but also for how the data are collected. The daily operations of the project are largely student led and run. To complete the remote, high-resolution verification, the students use Google Earth to display experimental weather data and geographic information databases, such as digital phonebooks. Using these data, the students then make verification phone calls to residences and businesses, throughout the United States, thought to have been affected by a severe thunderstorm. The present article summarizes the data collection facilities and techniques, discusses applications of these data, and shows comparisons of SHAVE reports to reports currently available from Storm Data.

Available online at http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175/2009BAMS2815.1.

Ortega, K. L., J. J. Gourley, K. M. Kuhlman, K. L. Manross, T. M. Smith, 2011: Lessons learned and future goals for high-resolution severe storm verification at the National Severe Storms Laboratory. Preprints, The Conference on Weather Warnings and Communication, Oklahoma City, OK, USA, American Meteorological Society, 2.3.

The National Severe Storms Laboratory has conducted the Severe Hazards Analysis and Verification Experiment (SHAVE) each summer since 2006. The primary goal of SHAVE is to collect high spatial density verification of hail, wind damage and flash flooding resulting from severe convective storms. These data have been used to verify experimental warnings, and evaluate remote sensing detection techniques and new gridded products. These data include reports of non-severe and null events which allows for a more complete understanding of the events resulting from a storm. There are two primary goals in the future for SHAVE: 1) dual polarized radar verification and 2) public warning response. Examples of collected data, verification/evaluation studies and future applications will be presented.

Available online at http://ams.confex.com/ams/39BROADCAST/webprogram/Paper189510.html.

Pal, N. R., A. K. Mandal, S. Pal, J. Das, V. Lakshmanan, 2006: Fuzzy Rule-Based Approach for Detection of Bounded Weak-Echo Regions in Radar Images. Journal of Applied Meteorology, 45, 1304-1312.

A method for the detection of a bounded weak-echo region (BWER) within a storm structure that can help in the prediction of severe weather phenomena is presented. A fuzzy rule-based approach that takes care of the various uncertainties associated with a radar image containing a BWER has been adopted. The proposed technique automatically finds some interpretable (fuzzy) rules for classification of radar data related to BWER. The radar images are preprocessed to find subregions (or segments) that are suspected candidates for BWERs. Each such segment is classified into one of three possible cases: strong BWER, marginal BWER, or no BWER. In this regard, spatial properties of the data are being explored. The method has been tested on a large volume of data that are different from the training set, and the performance is found to be very satisfactory. It is also demonstrated that an interpretation of the linguistic rules extracted by the system described herein can provide important characteristics about the underlying process.

Palmer, R. D., T. Y. Yu, G. Zhang, P. B. Chilson, M. I. Biggerstaff, M. B. Yeary, S. M. Torres, J. E. Crain, Y. Zhang, 2007: Weather radar education at the University of Oklahoma: An integrated inter-disciplinary approach. Proc. 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P13B.10.

In recent years, the University of Oklahoma (OU) has invested heavily in the development of a strategic research initiative in radar meteorology. Several new faculty members, with interests in weather radar, have joined both the School of Meteorology (SoM) and the School of Electrical and Computer Engineering (ECE). This inter-disciplinary group of energetic meteorologists and engineers has established the Atmospheric Radar Research Center (ARRC). The ARRC supports a broad portfolio of research interests, including radar polarimetry, phased array radar, profiling radar, advanced signal processing, retrieval algorithms, clutter mitigation, severe storm observations and detection, quantitative precipitation estimation, and general studies of atmospheric physics. In addition to research, one of the fundamental goals of the ARRC is providing OU students with a comprehensive, challenging education in the area of radar meteorology, emphasizing both the engineering and meteorological aspects of the field. We achieve our educational goals, in part, by the creation and continual maintenance of a synergistic curriculum exploiting the complementary disciplines of meteorology and electrical/computing engineering. As an integral component of OU's radar program, an innovative and coherent sequence of radar-related courses has been developed which serves both our undergraduate and graduate educational goals. This novel curriculum is not independent of, but forms an important component of the more traditional curricula of the two disciplines. Given the importance of weather radar for many observational studies of atmospheric phenomena, it is essential to include a significant hands-on experience for the students. Our curriculum provides a complete theoretical framework with which to understand weather radar theory while also providing access to local weather radar systems. In close collaboration with our NOAA partners at the National Severe Storms Laboratory (NSSL), we have developed laboratory modules for many of the radar courses using the C-band SMART radars, the S-band phased array radar, and the S-band KOUN polarimetric Doppler radar. Experimental design, operation, data analysis, and interpretation are emphasized. A description of the curriculum development effort will be provided. In addition, example laboratory modules will be presented emphasizing the practical aspects of this program.

Available online at http://ams.confex.com/ams/pdfpapers/123307.pdf.

Palmer, R., G. Zhang, M. Biggerstaff, P. Chilson, J. Crain, S. Torres, M. Yeary, T. Y. Yu, Y. Zhang, 2007: University Profile: Atmospheric Radar Research Center at the University of Oklahoma. IEEE Trans. Geosci. Remote Sensing. Newsletter, 1, 10-16.

Available online at http://www.grss-ieee.org/files/grsNL0307.pdf.

Palmer, R., K. Le, B. Isom, S. Torres, 2009: Spatial filtering of wind turbine clutter using adaptive phased array radars. Preprints, 25th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, 8B.6.

Palmer, R., M. Yeary, M. Biggerstaff, P. Chilson, J. Crain, K. Droegemeier, Y. Hong, A. Ryzhkov, T. Schuur, S. Torres, T. Yu, G. Zhang, Y. Zhang, 2009: Weather radar education at the University of Oklahoma: An integrated interdisciplinary approach. Bulletin of the American Meteorological Society, 90, 1277-1282.

Palmer, R. D., D. Bodine, M. R. Kumjian, B. Cheong, G. Zhang, Q. Cao, H. B. Bluestein, A. V. Ryzhkov, T. Y. Yu, Y. Wang, 2011: Observations of the 10 May 2010 tornado outbreak using OU-PRIME: Potential for new science with high-resolution polarimetric radar. Bulletin of the American Meteorological Society, 92, 871-891.

A tornado outbreak occurred in central Oklahoma on 10 May 2010, including two tornadoes with enhanced Fujita scale ratings of 4 (EF-4). Tragically, three deaths were reported along with significant property damage. Several strong and violent tornadoes occurred near Norman, Oklahoma, which is a major hub for severe storms research and is arguably one of the best observed regions of the country with multiple Doppler radars operated by both the federal government and the University of Oklahoma (OU). One of the most recent additions to the radars in Norman is the high-resolution OU Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME). As the name implies, the radar is used as a platform for research and education in both science and engineering studies using polarimetric radar. To facilitate usage of the system by students and faculty, OU-PRIME was constructed adjacent to the National Weather Center building on the OU research campus. On 10 May 2010, several tornadoes formed near the campus while OU researchers were operating OU-PRIME in a sector scanning mode, providing polarimetric radar data with unprecedented resolution and quality. In this article, the environmental conditions leading to the 10 May 2010 outbreak will be described, an overview of OU-PRIME will be provided, and several examples of the data and possible applications will be summarized. These examples will highlight supercell polarimetric signatures during and after tornadogenesis, and they will describe how the polarimetric signatures are related to observations of reflectivity and velocity.

Palucki, J. L., M. I. Biggerstaff, D. R. MacGorman, T. Schuur, 2011: Comparison between low-flash and non-lightning-producing convective areas within a mature mesoscale convective system. Weather and Forecasting, 26, 468-486.

Two small multicellular convective areas within a larger mesoscale convective system that occurred on 20
June 2004 were examined to assess vertical motion, radar reflectivity, and dual-polarimetric signatures between
flash and non-flash-producing convection. Both of the convective areas had similar life cycles and
general structures. Yet, one case produced two flashes, one of which may have been a cloud-to-ground flash,
while the other convective area produced no flashes. The non-lightning-producing case had a higher peak
reflectivity up to 6 km. Hence, if a reflectivity-based threshold were used as a precursor to lightning, it would
have yielded misleading results. The peak upward motion in the mixed-phase region for both cases was
8 m/s or less. However, the lightning-producing storm contained a wider region where the updraft exceeded
5 m/s. Consistent with the broader updraft region, the lightning-producing case exhibited a distinct graupel
signature over a broader region than the non-lightning-producing convection. Slight differences in vertical
velocity affected the quantity of graupel present in the mixed-phase region, thereby providing the subtle
differences in polarimetric signatures that were associated with lightning activity. If the results here are
generally applicable, then graupel volume may be a better precursor to a lightning flash than radar reflectivity.
With the dual-polarimetric upgrade to the national observing radar network, it should be possible to better
distinguish between lightning- and non-lightning-producing areas in weak convective systems that pose
a potential safety hazard to the public

Park, H. S., A. V. Ryzhkov, D. S. Zrnic, K. E. Kim, 2007: Optimization of the matrix of weights in the polarimetric algorithms for classification of radar echoes. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P11B.12.

Park, H., A. Ryzhkov, D. Zrnic, K. Kim, 2009: The hydrometeor classification algorithm for the polarimetric WSR-88D. Description of application to an MCS.. Weather and Forecasting, 24, 730-748.

Park, H., A. Ryzhkov, H. Reeves, T. Schuur, 2009: Classification of precipitation types during transitional winter weather using the RUC model and polarimetric radar retrievals. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, P2.20.

Available online at http://ams.confex.com/ams/pdfpapers/155580.pdf.

Parker, D. J., M. W. Douglas, M. Christoph, A. H. Fink, S. Janicot, J. B. Ngamini, E. Afiesimama, A. Agusti-Panareda, A. Beljaars, F. Dide, A. Ddiedhiou, T. Lebel, J. Polcher, J. L. Redelsperger, C. Thorncroft, G. Wilson, 2008: The Amma radiosonde programme and its implications for the future of atmospheric monitoring over Africa.. Preprints, 28th Conference on Hurricanes and Tropical Meteorology, Orlando, FL, USA, American Meteorological Society, 3C.1.

This presentation describes the upper air observational programme which is being carried out as part of the African Monsoon Multidisciplinary Analysis (AMMA). An important goal of AMMA is to evaluate the impact of the upper-air data on weather and climate prediction for West Africa, and for the hurricane genesis regions of the tropical Atlantic. Since 2004, AMMA scientists have been working with operational agencies in Africa to reactivate silent radiosonde stations, to renovate unreliable stations, and to install new stations in regions of particular climatic importance. A comprehensive upper air network of 21 stations, including four GCOS Upper Air Network (GUAN) stations, is now active over West Africa, and during the AMMA Special Observing Period (SOP) June to September 2006 some 7000 soundings were made in the region, representing the greatest density of upper air observations ever since in the region, exceeding even the number of soundings made during the GATE programme of 1974. AMMA also encompassed a short, intensive campaign on a network of PILOT stations in the western part of the region, centered on Senegal. This activity both exposed the dilapidated state of the operational PILOT network in the region, and demonstrated that important upper air data can be collected at relatively low cost through PILOT soundings. Many operational lessons were learned in AMMA, involving technical problems in the harsh environment of sub-Saharan Africa and issues of funding, coordination and communication among the many nations and agencies involved. From these lessons we are able to make firm recommendations for the maintenance and operation of a useful upper air network in WMO Region I in the future.

Parker, D. J., A. Fink, S. Janicot, J. Ngamini, M. W. Douglas, E. Afiesimama, A. Agusti-Panareda, A. Beljaars, F. Dide, A. Diedhiou, T. Lebel, J. Polcher, J. L. Redelsperger, C. Thorncroft, G. A. Wilson, 2008: The Amma Radiosonde Program and its Implications for the Future of Atmospheric Monitoring Over Africa. Bulletin of the American Meteorological Society, 89, 1015-1027.

This article describes the upper-air program, which has been conducted as part of the African Monsoon Multidisciplinary Analysis (AMMA). Since 2004, AMMA scientists have been working in partnership with operational agencies in Africa to reactivate silent radiosonde stations, to renovate unreliable stations, and to install new stations in regions of particular climatic importance. A comprehensive upper-air network is now active over West Africa and has contributed to high-quality atmospheric monitoring over three monsoon seasons. During the period June to September 2006 high-frequency soundings were performed, in conjunction with intensive aircraft and ground-based activities: some 7,000 soundings were made, representing the greatest density of upper air measurements ever collected over the region. An important goal of AMMA is to evaluate the impact of these data on weather and climate prediction for West Africa, and for the hurricane genesis regions of the tropical Atlantic. Many operational difficulties were encountered in the program, involving technical problems in the harsh environment of sub-Saharan Africa and issues of funding, coordination, and communication among the many nations and agencies involved. In facing up to these difficulties, AMMA achieved a steady improvement in the number of soundings received by numerical weather prediction centers, with a success rate of over 88% by August 2007. From the experience of AMMA, we are therefore able to make firm recommendations for the maintenance and operation of a useful upper-air network in WMO Region I in the future.

Payne, C., T. J. Schuur, D. R. MacGorman, W. D. Rust, M. Biggerstaff, K. Kuhlman, E. Bruning, N. Lund, 2008: Electrical and polarimetric radar observations of an HP supercell on 29 May 2004 during TELEX. Preprints, 3rd Conference on Meteorological Applications of Lightning Data, New Orleans, LA, USA, American Meteorological Society, 4.6.

Payne, C. D., T. J. Schuur, D. R. MacGorman, M. I. Biggerstaff, K. M. Kuhlman, W. D. Rust, 2010: Polarimetric and electrical characteristics of a lightning ring in a supercell storm. Monthly Weather Review, 138, 2405-2425.

On 30 May 2004, a supercell storm was sampled by a suite of instrumentation that had been deployed as part of the Thunderstorm Electrification and Lightning Experiment (TELEX). The instrumentation included the Oklahoma Lightning Mapping Array (OK-LMA), the National Severe Storms Laboratory S-band Weather Surveillance Radar-1988 Doppler (WSR-88D) polarimetric radar at Norman, Oklahoma, and two mobile C-band, Shared Mobile Atmospheric Research and Teaching Radars (SMART-R). Combined, datasets collected by these instruments provided a unique opportunity to investigate the possible relationships among the supercell’s kinematic, microphysical, and electrical characteristics. This study focuses on the evolution of a ring of lightning activity that formed near the main updraft at approximately 0012 UTC, matured near 0039 UTC, and collapsed near 0050 UTC. During this time period, an F2-intensity tornado occurred near the lightning-ring region. Lightning density contours computed over 1-km layers are overlaid on polarimetric and dual-Doppler data to assess the low- and midlevel kinematic and microphysical characteristics within the lightning-ring region. Results indicate that the lightning ring begins in the middle and upper levels of the precipitation-cascade region, which is characterized by inferred graupel. The second time period shows that the lightning source densities take on a horizontal u-shaped pattern that is collocated with midlevel differential reflectivity and correlation coefficient rings and with the strong cyclonic vertical vorticity noted in the dual-Doppler data. The final time period shows dissipation of the u-shaped pattern and the polarimetric signatures as well as an increase in the lightning activity at the lower levels associated with the development of the rear-flank downdraft (RFD) and the envelopment of the vertical vorticity maximum by the RFD.

Picca, J., A. Ryzhkov, 2012: A dual-wavelength polarimetric analysis of the 16 May 2010 Oklahoma City extreme hailstorm. Monthly Weather Review, 140, 1385-1403.

A comparative analysis of a supercell hailstorm using simultaneous observations with S-band and C-band polarimetric radars supported by abundant ground truth reports is presented in this study. The storm occurred on 16 May 2010 and produced a swath of extremely damaging hail across a large portion of the Oklahoma City metro area. Hail sizes over 10 cm in diameter and hail drifts upwards of 1.5 m in height were reported. Both S-band (KOUN) and C-band (OU-PRIME) polarimetric radars in Norman, OK sampled the storm at ranges less than 60 km, so that high-resolution dual-wavelength polarimetric data were obtained. Among the issues investigated in the study are the relation of hail size measured at the surface to the polarimetric signatures at both wavelengths, the difference between polarimetric signatures at the two wavelengths of hail aloft and near the surface (where melting hail is mixed with rain), and the three-body scattering signature (TBSS) associated with large hail.

Pietrafesa, L. J., K. Kelleher, M. Peng, S. Bao, 2006: A New Architecture For Coastal Inundation and Flood Warning Protection. Preprints, Marine Technology Society Conference, Boston, MA, USA, Marine Technology Society, 1-5.

Pietrafesa, L. J., K. Kelleher, T. Karl, M. Davidson, M. Peng, S. Bao, D. Dickey, L. Xie, H. Liu, M. Xia, 2007: A New Architecture For Coastal Inundation and Flood Warning Protection. Stemming the Tide of Coastal Disasters. Marine Technology Society Journal, 40, 71-77.

The marine atmosphere, coastal ocean, estuary, harbor and river water systems constitute a physically coupled system. while these systems have always been heavily impacted by coastal storms, increases in population density, infrastructure, and personal and business merchandise have exacerbated the economic and personal impacts of these events over the past half century. As such there has been increased focus on the need for more timely and accurate forecasts of impending events. Traditionally model forecast architectures for coastal storm surge, flooding and inundation of coastal and inland areas have taken the approach of dealing with each system separately: rivers, estuaries, harbors and offshore facing areas.
However, given advances in coupled modeling and the availability of real-time data, the ability to accurately predict and project coastal, estuary and inland flooding related to the passage of high energy and wet atmospheric events is rapidly emerging and requires a new paradigm in
system architecture. No longer do monthly averaged winds or river discharge or water levels have to be invoked in developing hindcasts for planning purposes or for real-time forecasts. In 1999 a hurricane associated flood on the North Carolina coast took 56 lives and caused more than $6 billion in economic impacts. None of the models existing at that time were able to properly forecast the massive flooding and clearly called for a new model paradigm. Here we propose a model system that couples atmospheric information to fully three dimensional, non-linear time dependent ocean basin, coastal and estuary hydrodynamic models coupled to interactive river models with input of real or modeled winds, observed or modeled precipitation, measured and modeled water levels, and streamflow. The river and
estuarine components must both be capable of going into modes of storage or accelerated discharge. Spatial scales must downscale in the horizontal from thousands to tens meters and in the vertical from hundreds to several centimeters. Topography and elevation data should be of the highest resolution available, necessary for highly accurate predictions of the timing and location of the inundation and retreat of flood waters. Precipitation information must be derived from the optimal mix of direct radar, satellite and ground-based observations. Creating the capability described above will advance the modernization of hydrologic services provided by the National Oceanic & Atmospheric Administration and provide more accurate and timely forecasts and climatologies of coastal and estuary flood-
ing. The goal of these climatologies and improved forecasts is to provide better information to local and regional planners, emergency managers, highway patrols and to improve the capacity of coastal communities to mitigate against the impacts of coastal flooding.

Pinto, J., C. Kessinger, B. Hendrickson, D. Megenhardt, P. Harasti, Q. Xu, P. Zhang, Q. Zhao, M. Frost, J. Cook, S. Potts, 2007: Storm characterization and short term forecasting potential using a phase array radar. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, Amer. Meteor. Soc., P5.18.

Available online at http://ams.confex.com/ams/pdfpapers/123703.pdf.

Priegnitz, D. L., D. E. Forsyth, 2006: The Radar Control Interface for the National Weather Radar Testbed. Extended Abstracts, 22nd International Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, American Meteorological Society, 11.2. [Available from David Priegnitz, National Severe Storms Laboratory, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

The National Weather Radar Testbed (NWRT) in Norman Oklahoma is a national weather research facility consisting of a converted Navy SPY-1 phased-array radar system. It is expected to be utilized by researchers both inside and outside the Norman area. One goal of the facility s to allow researchers to operate the radar and collect data without having to travel to Norman. A new Radar Control Interface (RCI) is being developed to simplify radar control and data collection operations. This paper describes the design and operation of the new RCI.

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_104391.htm.

Priegnitz, D. L., 2007: Update to the National Weather Radar Testbed Radar Control Interface. Preprints, 23rd International Conference on Interactive Information and Processing Systems (IIPS), San Antonio, TX, USA, American Meteorological Society, CD-ROM, 8A.2. [Available from David Priegnitz, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Significant improvements have been made to the National Weather Radar Testbed (NWRT) Radar Control Interface (RCI) over the past year to support research operations. The "look and feel" of the RCI has been modified to improve human-computer interaction. New process control functions have been implemented to better notify the operator of problems, allowing them to take corrective actions in a more timely manner. New processes have been added to simplify the building of scan control files, called "Stimulus Files", and integrating them into the system.

This paper describes in more detail the improvements to the RCI.

Available online at http://ams.confex.com/ams/87ANNUAL/techprogram/paper_117163.htm.

Priegnitz, D. L., P. L. Heinselman, C. D. Curtis, 2007: Dynamic scanning for the National Weather Radar Testbed. Extended Abstracts, 33rd International Radar Meteorology Conference, Cairns, Australia, American Meteorological Society, CD-ROM, 7.3. [Available from David Priegnitz, 120 David L Boren Blvd, Norman, OK, USA, 73072.]

During 2006 data collected on several convective storms with the National Weather Radar Testbed (NWRT) Phased Array Radar (PAR) demonstrated the benefits of scanning strategies based on higher temporal and spacial resolutions. The analysis of these data showed that increasing the temporal resolution of a volume scan could potentially benefit short-term forecasting by identifying rapidly changing features that would otherwise be missed with the longer scan times of conventional mechanically scanned radars (i.e., WSR-88D). Furthermore, the data collection demonstrated that storm location plays an important role in determining the best scanning strategy to use. For each of these events, a single pre-defined scanning strategy was chosen to meet the data collection goals at a given time. In many instances, it would have been desirable to "fine-tune" the scanning strategy by changing the number of elevation cuts, reducing azimuthal sector width, etc.

In this paper, changes to the NWRT software that allow "dynamic scanning" of convective events are discussed. Dynamic scanning allows the operator to update scan properties in real-time. It also provides the operator with the capability to schedule more than one scanning strategy (i.e., one or more focused rapid scan strategies followed by a surveillance scanning strategy). Preliminary results on the effectiveness of dynamic scanning used to support projects during the 2007 spring season will be discussed in the extended abstract.

Priegnitz, D., D. E. Forsyth, 2007: Update to the National Weather Radar Testbed Radar Control Interface. Preprints, The 23rd Conference on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 8A.2.

Priegnitz, D. L., P. L. Heinselman, S. M. Torres, R. Adams, 2009: Improvements to the National Weather Radar Testbed Radar Control Interface. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, NOAA/NSSL, CD-ROM, P10.10.

Since reported at the previous radar conference, significant enhancements have been made to the National Weather Radar Testbed (NWRT) phased array radar (PAR). As part of an ongoing effort, the radar control interface (RCI) has been improved to support system development, operations, and research. For example, as the adaptive scanning capabilities of the phased array radar are being explored and developed, further improvements to the RCI are being made to provide an effective interface between the PAR and the developers, scientists, and users.
This paper describes the improvements to the NWRT RCI and discusses the impacts of these in terms of increasing the usability of this unique radar system.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_155633.htm.

Priegnitz, D., S. Torres, P. Heinselman, 2012: An Adaptive Pedestal Control Algorithm for the National Weather Radar Testbed Phased Array Radar. Extended Abstracts, 28th Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, Amer. Meteor. Soc., CD-ROM, P1.7.

The National Weather Radar Testbed (NWRT) Phased Array Radar (PAR), located in Norman Oklahoma, consists of a single antenna array capable of electronically scanning a 90 degree azimuthal sector at any given moment. The antenna is mounted on a pedestal which can be commanded to move in any azimuthal direction allowing researchers to follow areas of interesting weather. Until now, when tracking a weather feature, an operator had to decide when and where to move the pedestal in order to keep the feature in the field of view, which imposed a significant operational burden. This paper describes an adaptive algorithm that uses reflectivity data to track an operator-defined weather feature and automatically adjusts the pedestal position to optimally keep it in the field of view.

Proud, J. L., K. K. Droegemeier, V. T. Wood, L. White, 2005: Optimal sampling strategies for hazardous weather detection using networks of dynamically adaptive Doppler radars. 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P10R.12.

Proud, J., K. K. Droegemeier, V. T. Wood, R. A. Brown, L. White, 2006: Optimum sampling strategies for hazardous weather detection using networks of dynamically adaptive Doppler radars. Preprints, Severe Local Storms Special Symposium, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P1.3.

In this paper, we explain our methods to determine the optimal adaptive scanning strategies for The Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) radars in order to extract the maximum amount of information for a particular purpose while minimizing the resources used. CASA is a National Science Foundation Engineering Research Center that was created in fall 2003 and is led by the University of Massachusetts at Amherst with several partners including the University of Oklahoma. CASA is establishing a revolutionary new paradigm in which systems of distributed, collaborative, and adaptive sensor (DCAS) networks are being developed to overcome fundamental limitations in current approaches – particularly the inability to sample the lower parts of the atmosphere.

In the first phase of its research program, CASA is placing test beds of small, inexpensive, low-power Doppler weather radars – sited on existing infrastructures such as cell phone towers – to test the DCAS concept. The first such network, called NETRAD and consisting of 4 dual-polarization, mechanically-scanning Doppler radars, will begin operating in central Oklahoma in fall 2005. This network will be expanded to 9 phased-array radars in late 2006. Unique to these systems is their ability to dynamically adjust their scanning strategies and other attributes, in a collaborative manner with neighboring radars, to sense multiple atmospheric phenomena while simultaneously meeting multiple end user needs – all in a theoretically optimal manner.

In order to find out how to optimally sample with the CASA radars, we will be modeling tornadoes, mesocyclones, and other storm features with idealized flows, such as a Burgers-Rott vortex, and then fitting the observations (initially simulated data) to these models. Many scanning strategies will be devised with varying parameters such as the azimuthal sampling interval, the distance from the radar to the center of the vortex, and the number of radars adaptively scanning both a single vortex as well as more than one vortex. In order to determine which scanning strategy is optimal, metrics for optimality, such as cost functions and probability density functions will be used.

Proud, J. L., K. K. Droegemeier, V. T. Wood, R. A. Brown, 2009: Sampling Strategies for Tornado and Mesocyclone Detection Using Dynamically Adaptive Doppler Radars: A Simulation Study. Journal of Atmospheric and Oceanic Technology, 26, 492-507.

Increasing tornado and severe storm warning lead time (lead time is defined here as the elapsed time between the issuance of a watch or warning and the time at which the anticipated weather event first impacts the specified region) through the use of radar observations has long been a challenge for researchers and operational forecasters. To improve lead time and the probability of detecting tornadoes while decreasing the false alarm ratio, a greater understanding, obtained in part by more complete observations, is needed about the region of storms within which tornadoes form and persist. Driven in large part by this need, but also by the goal of using numerical models to explicitly predict intense local weather such as thunderstorms, the National Science Foundation established, in fall 2003, the Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA). CASA is developing a revolutionary new paradigm of using a network of small, closely spaced, inexpensive, low-power dual-polarization Doppler weather radars to overcome the inability of widely spaced, high-power radars to sample large regions of the lower atmosphere owing to the curvature of earth given that zero or negative beam elevation angles are not allowed. Also, current radar technology operates mostly independently of the weather and end-user needs, thus producing valuable information on storms as a whole but not focused on any specific phenomenon or need. Conversely, CASA utilizes a dynamically adaptive sensing paradigm to identify, and optimally sample, multiple targets based upon their observed characteristics in order to meet a variety of often competing end-user needs.

The goal of this study is to evaluate a variety of adaptive sampling strategies for CASA radars to assess their effectiveness in identifying intense low-altitude vortices. Such identification, for the purposes of this study, is defined as achieving a best fit of simulated observations to an analytic model of a tornado or mesocyclone. Several parameters are varied in this study including the size of the vortex, azimuthal sampling interval, distance of the vortex from the radar, and radar beamwidth.

Results show that, in the case of small vortices, adaptively decreasing the azimuthal sampling interval (i.e., overlapping beams) is beneficial in comparison to conventional azimuthal sampling that is approximately equal to the beamwidth. However, the benefit is limited to factors of 2 in overlapping. When simulating the performance of a CASA radar in comparison to that of a Weather Surveillance Radar-1988 Doppler (WSR-88D) at close range, with both operating in the conventional nonoverlapping mode, the WSR-88D (with a beamwidth about half that of a CASA radar) performs better. However, when overlapping is applied to the CASA radar, for which little additional processing time is required, the results are comparable. In effect, the sampling resolution of a radar can be increased simply by decreasing the azimuthal sampling interval as opposed to installing a larger antenna.

Ramig, N., D. MacGorman, W. D. Rust, T. J. Schuur, E. Bruning, P. Krehbiel, W. Rison, T. Hamlin, J. Straka, C. Payne, I. Apostolakopoulos, M. Biggerstaff, N. Biermann, L. Carey, 2005: The stratiform region of an MCS on 19 June in TELEX 2004 observed with polarimetric and Doppler radars, electric field soundings, and a lightning mapping array. Preprints, AGU Fall Meeting, San Francisco, CA, USA, American Geophysical Union, AE21A-0977.

Ramig, N., D. MacGorman, D. Rust, T. Schuur, P. Krehbiel, W. Rison, T. Hamlin, J. Straka, M. Biggerstaff, 2007: Relationship between lightning location and polarimetric radar signatures in an MCS. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, IUGG/Commission on Atmospheric Electricity, PS5-2.

The relationship of lightning initiation and structure to the storm microphysics and structure depicted by polarimetric radar has been analyzed for a small mesoscale convective system (MCS) that occurred on 19 June 2004 during the Thunderstorm Electrification and Lightning Experiment (TELEX). Horizontal reflectivity (Z), differential reflectivity (Zdr), specific differential phase (Kdp) and correlation coefficient (ρHV) data were gathered by a 10-cm, polarimetric radar located in Norman, Oklahoma. Three-dimensional lightning structure was mapped by the Oklahoma Lightning Mapping Array (OK-LMA), and ground strike points were mapped by the United States National Lightning Detection Network. OK-LMA data were processed to group mapped points into flashes and to determine the initiation location of each flash that contained more than 10 mapped points. The initiation location was calculated by sequentially eliminating outliers among the first 10 points that occurred in a flash, with no fewer than 5 points being used in the final initiation location. The initiation location and mapped points for each flash were superimposed on polarimetric radar data in order to investigate lightning relationships with storm structure. The lightning initiation points tended to cluster together in one of two altitude ranges and were almost all in the convective line. Initial results show a relationship between the lightning initiation locations and radar signatures in both Z and Kdp. In the lower altitude range, between 3 and 5 km MSL, initiation locations tended to cluster around updraft cores, in regions characterized by a transition in Z from 50 to 55 dBZ and a transition in Kdp from 0.4 to 0.5 deg/km. In the upper range, between 8 and 10 km MSL, initiation points tended to cluster directly above the updrafts, in regions characterized by a transition in Z from 42.5 to 47.5 dBZ and in Kdp from 0.075 to 0.150 deg/km. The two-layer nature of the initiation points is consistent with grossly tripolar structure of the charge distribution involved in lightning in the convective line. Also, the horizontal pattern of the initiation locations has a quasi-periodic horizontal structure which is 180 degrees out of phase with the maximum updraft locations for the lower region and is in phase with the maximum updraft locations for the upper region. There were also a few flash initiations within the stratiform region, possibly associated with decaying cells. The values of Z and Kdp associated with these initiation points were smaller than in the convective line, but as in the convective line, the initiations also occurred along gradients, above a local maximum, in these parameters.

Ramsey, N. R., K. L. Ortega, V. Lakshmanan, 2011: A technique for spatial evaluation of severe thunderstorm warnings issued by the National Weather Service. Preprints, 27th Conference on Interactive Information Processing Systems, Seattle, WA, USA, American Meteorological Society, 372.

In 2007, the National Weather Service (NWS) changed severe weather warnings from county-based warnings to storm-based warnings. The primary goal of this change was to reduce the area under warning in order to reduce the perception of a false alarm by people unaffected by the storm in the warned counties. While the NWS changed the way in which warnings were issued, the method in which they verify warnings has remained the same. Warnings are verified by reports of hail 25.4mm in diameter, winds 58 mph or greater, reports of wind damage, such as broken tree limbs, or a tornado. Only one report within the temporal and spatial bounds of a warning is needed for verification. This type of warning verification might assist in knowing the percentage of severe weather events which were warned, but it offers no information on how much of the warning area was justified or how much of the area outside of the warning experienced severe weather. The National Severe Storms Laboratory (NSSL) has developed a number of multi-radar, multi-sensor severe weather products which could serve as a proxy in determining the accuracy and efficiency of severe storm warnings. The efficiency of NWS warnings will be studied through the use of time-accumulated swaths of hail size fields by assessing the placement of warnings with respect to storm motion and intensity. These warnings will then be compared to the daily composite of severe thunderstorm warnings to determine the efficiency of warnings on an individual basis versus daily scale.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper180808.html.

Reinoso-Rondinel, R., T. Yu, S. Torres, 2009: Task prioritization on phased-array radar scheduler for adaptive weather sensing. Extended Abstracts, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P10.13.

Reinoso-Rondinel, R., T. Yu, S. Torres, 2010: Task prioritization on phased‐array radar scheduler for adaptive weather sensing. Preprints, 26th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 14B.6.

Reinoso-Rondinel, R., T. Y. Yu, S. Torres, 2010: Multifunction phased‐array radar: time balance scheduler for adaptive weather sensing. Journal of Atmospheric and Oceanic Technology, 27, 1854-1867.

Reinoso-Rondinel, R., T. Yu, S. Torres, 2011: Performance evaluation of the time balance scheduling algorithm for phased-array radar adaptive weather sensing. Extended Abstracts, 27th Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Seattle, WA, USA, Amer. Meteor. Soc., CD-ROM, 368.

Phased array radars have the capability of dynamically controlling the beam position on a pulse-by-pulse basis, which allows a single radar to simultaneously perform multiple functions. The phased array radar (PAR) installed at the National Weather Radar Testbed (NWRT) in Norman, Oklahoma is the first phased array system in the nation dedicated to weather radar research and can electronically steer the beam in both azimuth and elevation. The concept of Time Balance (TB) was introduced and demonstrated in the previous work as a means to dynamically schedule multiple tasks of tracking and surveillance for adaptive weather sensing. Two quality measures were theoretically established to quantify the gain of adaptive sensing relative to the conventional Volume Coverage Pattern (VCP) used in the operational Weather Surveillance Radar-1988 Doppler (WSR-88D).
Here, the previous work is put in the context by establishing a complete scheduling framework that can be easily implemented for real-time operation on the NWRT PAR. The framework is modular and consists of four processes: (1) a storm identification algorithm, (2) a storm tracking algorithm, (3) a tasks configuration module, and (4) the TB scheduling algorithm. The storm identification algorithm automatically identifies 3D storm cells during the surveillance task so that updated information about the number, locations, and size of storm cells is provided to the tracking and TB algorithms. In this work, the same framework is used to simulate and evaluate the performance of the TB scheduling algorithm on multiple archived weather data cases. The performance of the TB scheduling algorithm can then be characterized by statistical analyses of the error between the theoretical and estimated quality measures. This is the 1st step towards a real-time implementation of the TB scheduling algorithm on the NWRT PAR, which will enable the demonstration of improvements that can be realized with focused, adaptive weather observations.

Richardson, Y. P., K. K. Droegemeier, R. P. Davies-Jones, 2007: The influence of horizontal environmental variability on numerically simulated convective storms: Part I: Variations in vertical shear. Monthly Weather Review, 135, 3429-3455.

Severe convective storms are typically simulated using either an idealized, horizontally homogeneous environment (i.e., single sounding) or an inhomogeneous environment constructed using numerous types of observations. Representing opposite ends of the spectrum, the former allows for the study of storm dynamics without the complicating effects of either land surface or atmospheric variability, though arguably at the expense of physical realism, while the latter is especially useful for prediction and data sensitivity studies, though because of its physical completeness, determination of cause can be extremely difficult. In this study, the gap between these two extremes is bridged by specifying horizontal variations in environmental vertical shear in an idealized, controlled manner so that their influence on storm morphology can be readily diagnosed. Simulations are performed using the Advanced Regional Prediction System (ARPS), though with significant modification to accommodate the analytically specified environmental fields. Several steady-state environments are constructed herein that retain a good degree of physical realism while permitting clear interpretation of cause and effect. These experiments are compared to counterpart control simulations in homogeneous environments constructed using single wind profiles from selected locations within the inhomogeneous environment domain. Simulations in which steady-state vertical shear varies spatially are presented for different shear regimes (storm types). A gradient of weak shear across the storm system leads to preferred cell development on the flank with greater shear. In a stronger shear regime (i.e., in the borderline multicell/supercell regime), however, cell development is enhanced on the weaker shear flank while cell organization is enhanced on the strong shear side. When an entire storm system moves from weak to strong shear, changes in cell structure are influenced by local mesoscale forcing associated with the cold pool. In this particular experiment, cells near the leading edge of the cold pool, where gust front convergence occurs along a continuous line, evolve into a bow-echo structure as the shear increases. In contrast, simulated cells that remain relatively isolated on the flank of the cold pool tend to develop supercellular characteristics.

Rust, W. D., D. R. MacGorman, T. J. Schuur, P. Krehbiel, T. Hamlin, M. Biggerstaff, L. Carey, J. Straka, C. Payne, A. Caine, 2005: The stratiform region of an MCS on 19 June in TELEX 2004 observed with polarimetric radar, electric field soundings, and a lightning mapping array. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, J3J.5.

Ryzhkov, A. V., T. J. Schuur, D. W. Burgess, D. S. Zrnic, 2005: Polarimetric tornado detection. Journal of Applied Meteorology, 44, 557-570.

Ryzhkov, A. V., S. E. Giangrande, T. J. Schuur, 2005: Rainfall estimation with a polarimetric prototype of WSR-88D. Journal of Applied Meteorology, 44, 502-515.

Ryzhkov, A. V., T. J. Schuur, D. W. Burgess, P. L. Heinselman, S. E. Giangrande, D. S. Zrnic, 2005: The Joint Polarization Experiment: Polarimetric rainfall measurements and hydrometeor classification. Bulletin of the American Meteorological Society, 86, 809-824.

2007 Office of Atmospheric Research (OAR) Outstanding Scientific Paper Award

Ryzhkov, A. V., S. E. Giangrande, V. M. Melnikov, T. J. Schuur, 2005: Calibration Issues of Dual-Polarization Radar Measurements. Journal of Atmospheric and Oceanic Technology, 22, 1138-1155.

Ryzhkov, A. V., D. S. Zrnic, 2005: Radar Polarimetry at S, C, and X bands. Comparative Analysis and Operational Implications. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, 9R.3.

Ryzhkov, A. V., 2005: On the Use of Differential Phase for Polarimetric Rainfall Measurements. A New Approach to Kdp Estimation. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P9R.8.

Ryzhkov, A. V., 2007: The impact of beam broadening on the quality of radar polarimetric data. Journal of Atmospheric and Oceanic Technology, 24, .

Ryzhkov, A. V., D. S. Zrnic, 2007: Depolarization in ice crystals and its effect on radar polarimetric measurements. Journal of Atmospheric and Oceanic Technology, 24, .

Ryzhkov, A. V., D. S. Zrnic, P. Zhang, J. Krause, H. Park, D. Hudak, J. Young, J. L. Alford, M. Knight, J. W. Conway, 2007: Comparison of polarimetric algorithms for hydrometeor classifcation at S and C bands. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, 10.3.

Ryzhkov, A. V., P. Zhang, D. Hudak, J. L. Alford, M. Knight, J. W. Conway, 2007: Validation of polarimetric methods for attenuation correction at C band. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P11B.12.

Ryzhkov, A., J. Y. Gu, P. Zhang, P. Neilley, M. Knight, B. Wolf, D. I. Lee, 2008: C-band polarimetric observations of winter storms in the US Midwest. Extended Abstracts, 5th European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Vaisala, CD-ROM, 3.1.

Ryzhkov, A., S. Giangrande, A. Khain, M. Pinsky, A. Pokrovsky, 2008: Exploring model-based polarimetric retrieval of vertical profiles of precipitation. Extended Abstracts, 5th European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Vaisala, CD-ROM, P6.1.

Ryzhkov, A., G. Zhang, S. Luchs, L. Ryzhkova, 2008: Polarimetric characteristics of snow measured by radar and 2D video disdrometer. Extended Abstracts, 5th European Conference on Radar in Meteorology and Hydrology, Helsinki, Finland, Vaisala, CD-ROM, P6.5.

Ryzhkov, A., S. Ganson, A. Khain, M. Pinsky, A. Pokrovsky, 2009: Polarimetric characteristics of melting hail at S and C bands. Extended Abstracts, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, 4A.6.

Available online at http://ams.confex.com/ams/pdfpapers/155571.pdf.

Ryzhkov, A., M. Pinsky, A. Pokrovsky, A. Khain, 2011: Polarimetric radar observation operator for a cloud model with spectral microphysics. Journal of Applied Meteorology and Climatology, 50, 873-894.

Sachidananda, M., D. S. Zrnic, 2006: Ground Clutter Filtering Dual_polarized, Staggered PRT Sequnece-. Journal of Atmospheric and Oceanic Technology, 23, 1114-1130.

A procedure to filter the ground clutter from a dual polarized staggered PRT sequence and recover the complex spectral coefficients of the weather signal is presented. While magnitude spectra are sufficient for estimation of the spectral moments from staggered PRT sequences, computation of differential phase in dual polarized radars requires recovery of the complex spectra. Herein a method is given to recover the complex spectral coefficients after the ground clutter is filtered. Under the condition of "narrow" spectra, it is possible to recover the differential phase, ФDP, and the copolar correlation coefficient, ρhv accurately, in addition to the differential reflectivity, ZDR. The technique is tested on simulated time series and on actual radar data. The efficacy of the method is demonstrated on PPI plots of polarimetric variables.

Santos, P., K. Carey, W. MacKenzie, J. Zhang, R. Ferraro, J. Yoe, 2007: Summary of Global Positioning System (GPS) Integrated Precipitable Water (IPW). NWA Elec. J. Op. Met., EJ4, x-x.

Saxion, D. S., R. D. Rhoton, R. L. Ice, D. A. Warde, O. E. Boydstun, S. M. Torres, G. Meymaris, W. D. Zittel, 2007: New science for the WSR-88D: implementing a major mode on the SIGMET RVP8. Preprints, 23rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, AMS, CD-ROM, P2.9.

Saxion, D. S., R. D. Rhoton, R. L. Ice, J. C. Krause, O. E. Boydstun, W. D. Zittel, S. M. Torres, D. A. Warde, 2009: New science for the WSR-88D: staggered PRT implementation on the SIGMET RVP8. Preprints, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, CD-ROM, P5.1.

The NEXRAD WSR-88D Radar Operations Center (ROC) is responsible for implementing new signal processing algorithms planned for deployment in the Open Radar Data Acquisition (ORDA) System. The overarching goal of these new signal processing algorithms is to improve data quality. After the successful deployment of the Sachidananda/Zrnic Phase Coding algorithm (SZ-2) which mitigates range folding and Clutter Mitigation Decision (CMD) algorithm which dynamically identifies ground clutter, the ROC is implementing the Staggered Pulse Repetition Time (SPRT) algorithm developed at the National Severe Storms Laboratory (NSSL) to mitigate velocity aliasing. The ROC is following a three phased approach for the design and implementation of SPRT. The first phase provided requirement analysis, specifications, and the architectural foundation needed to implement the SPRT algorithm into the ORDA. The second phase provided early design, implementation, and engineering testing for an engineering analysis of the SPRT algorithm with a simple mean-level-removal clutter filter. The third phase will provide an operational version of SPRT utilizing a spectral clutter filter. This paper will illustrate the benefits of SPRT and present the progression through the three phases of the SPRT implementation for the WSR-88D.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_155158.htm.

Scharfenberg, K. A., V. Lakshmanan, S. E. Giangrande, 2005: Development and testing of polarimetric radar applications in WDSS-II. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 5.1.

Scharfenberg, K. A., D. J. Miller, T. J. Schuur, P. T. Schlatter, S. E. Giangrande, V. M. Melnikov, D. W. Burgess, D. L. Andra, Jr., M. P. Foster, J. M. Krause, 2005: The Joint Polarization Experiment: Polarimetric radar in forecasting and warning decision-making. Weather and Forecasting, 20, 775-788.

To test the utility and added value of polarimetric radar products in an operational environment, data from the Norman, Oklahoma (KOUN), polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) were delivered to the National Weather Service Weather Forecast Office (WFO) in Norman as part of the Joint Polarization Experiment (JPOLE). KOUN polarimetric base data and algorithms were used at the WFO during the decision-making and forecasting processes for severe convection, flash floods, and winter storms. The delivery included conventional WSR-88D radar products, base polarimetric radar variables, a polarimetric hydrometeor classification algorithm, and experimental polarimetric quantitative precipitation estimation algorithms. The JPOLE data collection, delivery, and operational demonstration are described, with examples of several forecast and warning decision-making successes. Polarimetric data aided WFO forecasters during several periods of heavy rain, numerous large-hail-producing thunderstorms, tornadic and nontornadic supercell thunderstorms, and a major winter storm. Upcoming opportunities and challenges associated with the emergence of polarimetric radar data in the operational community are also described.

Scharfenberg, K. A., K. L. Elmore, E. Forren, V. Melnikov, D. S. Zrnic, 2005: Estimating the impact of a 3-dB sensitivity loss on WSR-88D data. Preprints, 32nd Conf. on Radar Meteorology, Albuquerque, NM, USA, Amer. Meteor. Soc., CD-ROM, P12R.9.

The planned upgrade of the WSR-88D network to include dual-polarimetric capabilities is expected to result in a loss of about 3 dB in sensitivity per channel. In order to better estimate the impact of this sensitivity loss, case study and real-time simulations were performed.

Algorithm products and base data from six archive WSR-88D cases were examined. The proportion of reflectivity samples lost upon desensitization was calculated, and the visibility of important meteorological features and velocity dealiasing errors before and after the desensitization were noted. Changes in the outputs of the echo top, hail detection, and legacy mesocyclone algorithms were observed. Changes to the output of the VAD wind profile (VWP) algorithm were measured. These results are presented.

In addition, a 3 dB higher threshold then usual was applied to KTLX WSR-88D data to simulate the signal loss. This data was then made available to National Weather Service forecasters for a side-by-side evaluation during the spring 2005 convective season. Forecaster feedback was compiled to estimate the impact of the sensitivity loss on situation awareness and decision-making, and these results are discussed.

An overview of proposed mitigation techniques to recover some of the lost velocity information is presented.

Available online at http://ams.confex.com/ams/pdfpapers/96931.pdf.

Scharfenberg, K. A., K. L. Elmore, T. J. Schuur, C. Legett, 2007: Analysis of dual-pol WSR-88D base data collected during three significant winter storms. Preprints, 31st Intl. Conf. on Radar Meteor., Cairns, Australia, Amer. Meteor. Soc., CD-ROM, P10.10.

Base data from a dual-pol WSR-88D radar collected during three significant winter storms in Oklahoma are examined. These cases (29-30 November 2006, 12-14 January 2007, and 20 January 2007) were chosen due to concurrent collection of high-resolution surface precipitation type reports near the radar (see paper by Elmore, Scharfenberg, and Legett). Large temporal and spatial variabilities in precipitation types were observed during these events as revealed by the surface reports. This paper will focus on radar data collected during these periods of large variability. Associating the evolution of the radar data and the surface reports is critical for future enhancements to automated hydrometeor classification and to successful forecast decision-making during winter storms.

Available online at http://ams.confex.com/ams/pdfpapers/123618.pdf.

Scharfenberg, K., T. M. Smith, C. Legett, K. L. Manross, K. L. Ortega, A. G. Kolodziej, 2008: NSSL's prototype enhanced severe thunderstorm database. Extended Abstracts, 24th Conf. on IIPS, New Orleans, LA, USA, Amer. Meteor. Soc., 5C.1.

Schmit, T. J., R. M. Rabin, A. S. Bachmeier, J. Li, M. M. Gunshor, H. Steigerwaldt, A. J. Schreiner, R. Aune, G. J. Wade, 2009: Many uses of the geostationary operational environmental satellite-10 Sounder and Imager during a High Inclination State.. J. Applied Remote Sensing, 3, .

Available online at http://spiedl.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=JARSC4000003000001033514000001&idtype=cvips&prog=normal.

Schultz, D. M., K. M. Kanak, J. M. Straka, R. J. Trapp, B. A. Gordon, D. S. Zrnic, G. H. Bryan, A. J. Durant, T. J. Garrett, P. M. Klein, D. K. Lilly, 2006: The mysteries of mammatus clouds: Observations and formation mechanisms. Journal of the Atmospheric Sciences, 63, 2409-2435.

Mammatus clouds are an intriguing enigma of atmospheric fluid dynamics and cloud physics. Most commonly observed on the underside of cumulonimbus anvils, mammatus also occur on the underside of cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus, as well as in contrails from jet aircraft and pyrocumulus ash clouds from volcanic eruptions. Despite their aesthetic appearance, mammatus have been the sub ject of few quantitative research studies. Observations of mammatus have been obtained largely through serendipitous opportunities with a single observ- ing system (e.g., aircraft penetrations, visual observations, lidar, radar) or tangential observations from field programs with other ob jectives. Theories describing mammatus remain untested as ad- equate measurements for validation do not exist because of the small distance scales and short time scales of mammatus. Modeling studies of mammatus are virtually nonexistent. As a result, relatively little is known about the environment, formation mechanisms, properties, microphysics, and dynamics of mammatus.

This paper presents a review of mammatus clouds that addresses these mysteries. Previous observations of mammatus and proposed formation mechanisms are discussed. These hypothesized mechanisms are anvil subsidence, subcloud evaporation/sublimation, melting, hydrometeor fallout, cloud-base detrainment instability, radiative effects, gravity waves, Kelvin-Helmholtz instability, Rayleigh-Taylor instability, and Rayleigh-Bénard-like convection. Other issues addressed in this paper include whether mammatus are composed of ice or liquid water hydrometeors, why mammatus are smooth, what controls the temporal and spatial scales and organization of individual mammatus lobes, and what are the properties of volcanic ash clouds that produce mammatus? The similarities and differences between mammatus, virga, stalactites, and reticular clouds are also discussed. Finally, because much still remains to be learned, research opportunities are described for using mammatus as a window into the microphysical, turbulent, and dynamical processes occurring on the underside of clouds.

Schultz, D. M., F. Zhang, 2007: Baroclinic development within zonally varying flows. Quarterly Journal of the Royal Meteorological Society, 133, 1101-1112.

Schuur, T. J., A. V. Ryzhkov, D. R. Clabo, 2005: Climatological analysis of DSDs in Oklahoma as revealed by a 2D-video disdrometer and polarimetric WSR-88D radar. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 15R.4.

Schuur, T. J., A. V. Ryzhkov, P. Zhang, 2005: Polarization characteristics of winter storms in Oklahoma. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P9R.13.

Schuur, T. J., A. V. Ryzhkov, S. Giangrande, 2006: Winter precipitation type classification with a polarimetric WSR-88D radar. Preprints, 12th Conference on Aviation, Range, and Aerospace Meteorology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P6.1.

Schuur, T. J., S. E. Giangrande, A. V. Ryzhkov, 2008: Polarimetric WSR-88D reflectivity and differential reflectivity attenuation correction for tropical rainfall. Preprints, International Symposium of Weather Radar and Hydrology, Grenoble, France, Europole Congress Center, P1-021.

Schuur, T. J., H. S. Park, A. V. Ryzhkov, H. D. Reeves, 2012: Classification of precipitation types during transitional winter weather using the RUC model and polarimetric radar retrievals. Journal of Applied Meteorology and Climatology, 51, 763-779.

A new hydrometeor classification algorithm that combines thermodynamic output from the Rapid Update Cycle (RUC) model with polarimetric radar observations is introduced. The algorithm improves upon existing classification techniques that rely solely on polarimetric radar observations by using thermodynamic information to help to diagnose microphysical processes (such as melting or refreezing) that might occur aloft. This added information is especially important for transitional weather events for which past studies have shown radar-only techniques to be deficient. The algorithm first uses vertical profiles of wet-bulb temperature derived from the RUC model output to provide a background precipitation classification type. According to a set of empirical rules, polarimetric radar data are then used to refine precipitation-type categories when the observations are found to be inconsistent with the background classification. Using data from the polarimetric KOUN Weather Surveillance Radar-1988 Doppler (WSR-88D) located in Norman, Oklahoma, the algorithm is tested on a transitional winter-storm event that produced a combination of rain, freezing rain, ice pellets, and snow as it passed over central Oklahoma on 30 November 2006. Examples are presented in which the presence of a radar bright band (suggesting an elevated warm layer) is observed immediately above a background classification of dry snow (suggesting the absence of an elevated warm layer in the model output). Overall, the results demonstrate the potential benefits of combining polarimetric radar data with thermodynamic information from numerical models, with model output providing widespread coverage and polarimetric radar data providing an observation-based modification of the derived precipitation type at closer ranges.

Schwartz, C. S., J. S. Kain, S. J. Weiss, M. Xue, D. R. Bright, F. Kong, K. W. Thomas, J. J. Levit, M. C. Coniglio, 2009: Next-day convection-allowing WRF model guidance: A second look at 2 vs. 4 km grid spacing. Monthly Weather Review, 137, 3351-3372.

During the 2007 NOAA Hazardous Weather Testbed (HWT) Spring Experiment, the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma produced convection-allowing forecasts from a single deterministic 2 km model and a 10-member 4 km resolution ensemble. In this study, the 2 km deterministic output was compared with forecasts from the 4 km ensemble control member. Other than the difference in horizontal resolution, the two sets of forecasts featured identical WRFARW configurations, including vertical resolution, forecast domain, initial and lateral boundary conditions, and physical parameterizations. Therefore, forecast disparities were attributed solely to differences in horizontal grid spacing.

This study is a follow-up to similar work that was based on results from the 2005 Spring Experiment. Unlike the 2005 Experiment, however, model configurations were more rigorously controlled in the present study, providing a more robust dataset and a cleaner isolation of the dependence on horizontal resolution. Additionally, in this study, the 2 and 4 km output were compared to 12 km forecasts from the North American Mesoscale (NAM) model.

Model forecasts were analyzed using objective verification of mean hourly precipitation and visual comparison of individual events, primarily during the 21- to 33-hour forecast period to examine the utility of the models as next-day guidance. On average, both the 2 and 4 km model forecasts showed substantial improvement over the 12 km NAM. However, although the 2 km forecasts produced more detailed structures on the smallest resolvable scales, the patterns of convective initiation, evolution, and organization were remarkably similar to the 4 km output. Moreover, on average, metrics such as equitable threat score, frequency bias, and fractions skill score revealed no statistical improvement of the 2 km forecasts compared to the 4 km forecasts. These results, based on the 2007 dataset, corroborate previous findings, suggesting that decreasing horizontal grid spacing from 4 to 2 km provides little added value as next-day guidance for severe convective storm and heavy rain forecasters in the United States.

Schwartz, C. S., J. S. Kain, S. J. Weiss, D. R. Bright, M. Xue, F. Kong, K. W. Thomas, J. J. Levit, M. C. Coniglio, 2008: Next-day convection-allowing WRF model guidance: A second look at 2- vs. 4-km grid spacing. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, P10.3. [Available from Jack Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142052.htm.

Schwartz, C. S., J. S. Kain, D. R. Bright, S. J. Weiss, M. Xue, F. Kong, J. J. Levit, M. C. Coniglio, M. S. Wandishin, 2008: Toward improved convection-allowing ensembles: Model physics sensitivities and optimizing probabilistic guidance with small ensemble membership. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 13A.6. [Available from Jack Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142048.htm.

Schwartz, C. S., J. S. Kain, D. R. Bright, S. J. Weiss, M. Xue, F. Kong, J. J. Levit, M. C. Coniglio, M. S. Wandishin, 2009: Optimizing probabilistic high resolution ensemble guidance for hydrologic prediction. Preprints, 23rd Conference on Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, 9.4.

Available online at http://ams.confex.com/ams/89annual/techprogram/paper_147171.htm.

Scipion, D. E., R. D. Palmer, P. B. Chilson, E. Fedorovich, R. J. Doviak, G. Zhang, A. M. Botnick, 2009: Effects of Horizontal Shear of Vertical Velocity in DBS and SA Mean Wind Estimates Revealed by a Combination of LES and Virtual Radar. Extended Abstracts, AMS 89th Annual Conference, Phoenix, AZ, USA, AMS, 1-11.

Sen Roy, S., V. Lakshmanan, S. Roy Bhowmik, S. Thampi, 2010: Doppler weather radar based nowcasting of cyclone ogni. J. Earth Syst. Sci., 119, 183-199.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/dwrogni.pdf.

Sen Roy, S., V. Lakshmanan, S. Roy Bhowmik, S. Thampi, 2010: `Doppler weather radar based nowcasting of cyclone ogni. J. Earth Syst. Sci., 119, 183-199.

Seo, D. J., C. R. Kondragunta, K. Howard, S. V. Vasiloff, J. Zhang, 2005: The National Mosaic and Multisensor QPE (NMQ) Project-Status and plans for a community testbed for high-resolution multisensor quantitative precipitation estimation (QPE) over the United States. Preprints, 19th Conference on Hydrology, San Diego, CA, USA, American Meteorological Society, CD-ROM, 1.3.

Seo, D. J., C. R. Kondragunta, K. Howard, S. Vasiloff, J. Zhang, 2005: The national mosaic and multisensor QPE (NMQ) project-status and plans for a community testbed for high-resolution multisensor quantitative precipitation estimation (QPE) over the United States. Preprints, 19th Conf. on Hydrology, San Diego, CA, USA, Amer. Meteor. Soc., CD-ROM, 1.3.

Smith, T. M., V. Lakshmanan, 2006: Utilizing Google Earth as a GIS platform for weather applications. Preprints, 22nd Conference on Interactive Information Processing Systems, Atlanta, GA, USA, AMS, CD-ROM, 8.2.

Available online at http://ams.confex.com/ams/Annual2006/techprogram/paper_104847.htm.

Smith, T. M., P. L. Heinselman, D. Priegnitz, 2007: Characteristics of microburst events observed with the National Weather Radar Testbed phased array radar. Preprints, 23rd Conference on Interactive Information Processing Systems, San Antonio, TX, USA, AMS, CD-ROM, 7.8.

Microbursts are small-scale (< 4 km diameter) outflows induced by strong downdrafts in thunderstorms that frequently cause damage to property and are a hazard to aviators. Many severe microbursts originate from storm cells that form in regions of moderate-to-high Convective Available Potential Energy (CAPE), weak environmental shear, and environments that are highly unstable to downdraft formation. These storm cells typically have a life cycle of 20-40 minutes, which makes them very difficult to predict.

Automated algorithms that analyze radar data and make short-term predictions for microburst events, as well as detecting low-altitude divergence signatures associated with their outflows, have been implemented for WSR-88D and TDWR systems. These applications rely on microburst “precursors” that may be observed at the higher altitudes of a storm shortly preceding the outflow at the surface to make short-lead-time forecasts of a microburst event. However, microburst events evolve rapidly, and because these radars typically only sample the upper portions of a storm once every 4 to 6 minutes (depending on scanning strategy), they may not sample key precursor features aloft or the near-surface outflow.

This presentation examines damage-producing severe microburst events that occurred in Central Oklahoma during July 2006 that were observed with the National Weather Radar Testbed (NWRT) Phased Array Radar (PAR). These storms formed within 50 km of the PAR site and were sampled with a temporal resolution of 15 to 30 seconds. We will compare the PAR observations of the storms with the KTLX WSR-88D, OKC TDWR, and multi-radar, multi-sensor information from the Warning Decision Support System – Integrated Information.

Available online at http://ams.confex.com/ams/pdfpapers/120074.pdf.

Smith, T. M., V. Lakshmanan, 2008: Real-time and recent historical weather data in Google Earth. Extended Abstracts, 23rd Conference on Interactive Information Processing Systems, New Orleans, LA, USA, AMS, 9B.6.

The National Severe Storms Laboratory (NSSL) utilizes Google Earth as one of several ways to share experimental severe weather products with other researchers and operational meteorologists for evaluation and feedback. A variety of multi-sensor severe weather products are generated by NSSL and shared to Google Earth users via the internet at http://wdssii.nssl.noaa.gov. These products include spatially gridded fields of Vertically Integrated Liquid, Maximum Expected Hail Size, tracks of circulations derived from Doppler velocity data, composite reflectivity, and 30-to-60 minute forecast reflectivity fields, among others. These products, which have a spatial resolution of approximately 1 km by 1 km, are generated every one to five minutes within the Warning Decision Support System – Integrated Information (WDSS-II). The WDSS-II system provides the images in GeoTIFF format which may be imported into most Geographic Information Systems software including virtual globes such as Google Earth.

During the first two years these data have been provided on the internet, they have been used to improve the verification of severe weather events as well as in disaster response and post-event damage assessments. This presentation focuses on the scientific and educational uses of virtual globes to interrogate real-time and archived severe weather products.

Available online at http://ams.confex.com/ams/88Annual/techprogram/paper_134923.htm.

Smith, A. J., P. L. Heinselman, 2009: The impact of closely spaced elevation scans on observations obtained using the NWRT Phased Array Radar. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., P10.7.

Smith, A., P. Chilson, P. Heinselman, 2010: The impact of elevation scan spacing on observations of heat bursts sampled by the National Weather Radar Testbed Phased Array Radar. Extended Abstracts, 26th Conference on International Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., 15.B.`.

As part of the 2009 Phased Array Radar (PAR) Innovative Sensing Experiment (PARISE), a customized scanning strategy was developed using an unusually large number of elevation scans. This “dense sampling” strategy is intended to provide a large amount of vertical detail for analyzing hailstorms and other events. One such event is a heat burst, which is defined as a region of air that experiences significant warming as it descends rapidly. Heat bursts can create localized temperature spikes and dew point depressions of 10°C in as little as 15 min. People sensitive to heat may be threatened by this sudden change in temperature. Wind gusts of 25 m s-1 or higher may also occur, leading to potential property or agricultural damage. Because rapidly descending air precedes heat bursts, it is likely that analyses of detailed radar observations in elevation will lead to better understanding of how and when they may occur.

In the early morning hours of 13 May 2009, a series of heat bursts was observed by approximately 70 Oklahoma Mesonet stations. Rawinsonde data obtained from Norman, Oklahoma at 0000 UTC 13 May 2009 indicate a nearly dry-adiabatic lapse rate and relatively dry air between 750 and 400 mb. As thunderstorms moved into the region and dissipated, precipitation evaporated aloft and generated descent. The lapse rate allowed the descending air to increase in velocity and warm rapidly, resulting in heat bursts that spread over a large area. At 0320 UTC, a 15-min temperature increase of 8.0°C, dew point depression of 6.7°C and maximum wind gust of 23 m s-1 were observed in southwestern Oklahoma. Seven hours later, another 15-min temperature spike of 6.0°C, dew-point depression of 6.0°C and maximum wind gust of 15 m s-1 were observed in north-central Oklahoma. The other Mesonet stations reported weaker heat burst activity over this time period.

During this event, the NWRT PAR performed scans for a 2.5-hr period using the dense sampling strategy. To evaluate the usefulness of the closely spaced elevation scans, it is necessary to compare these results with those from a scan with fewer elevations. For this study, individual elevations will be selectively removed from the PAR dense sampling data to form a second “sparse” scan. Vertical cross-sections will be constructed at selected Mesonet sites, in order to demonstrate the detail obtained from both scans. Vertical reflectivity profiles will also be produced from both scans in order to provide a quantitative comparison of heat burst observations. The analysis will provide insight into which radar features are significant in analyzing and predicting heat burst activity. In addition, the results will provide guidance on how to implement PAR scanning when a large amount of vertical detail is necessary.

Smith, A., P. L. Heinselman, P. Chilson, 2010: Evaluation of rapid sampling rates using the National Weather Radar Testbed Phased-Array Radar. Extended Abstracts, Sixth European Conference on Radar Meteorology and Hydrology, Sibiu, Romania, National Meteorological Administration of Romania, 226-231.

Smith, T. M., V. Lakshmanan, 2011: Real-time, rapidly updating severe weather products for virtual globes. Computers and Geosciences, 37, 3-12.

It is critical that weather forecasters are able to put severe weather information from a variety of observational and modeling platforms into a geographic context so that warning information can be effectively conveyed to the public, emergency managers, and disaster response teams. The availability of standards for the specification and transport of virtual globe data products has made it possible to generate spatially precise, geo-referenced images and to distribute these centrally created products via a web server to a wide audience.
In this paper, we describe the data and methods for enabling severe weather threat analysis information inside a KML framework. The method of creating severe weather diagnosis products that are generated and translating them to KML and image files is described. We illustrate some of the practical applications of these data when they are integrated into a virtual globe display. The availability of standards for interoperable virtual globe clients has not completely alleviated the need for custom solutions. We conclude by pointing out several of the limitations of the general-purpose virtual globe clients currently available.

Smith, A. J., P. B. Chilson, P. L. Heinselman, 2011: Using the NWRT PAR to evaluate temporal sampling during two rapidly evolving tornado events. Preprints, 27th Interactive Information Processing Systems, Seattle, WA, USA, Amer. Meteor. Soc., 13B.4.

During severe weather events, a tornado may develop on the order of minutes or seconds. Operational radars such as the WSR-88D are capable of detecting tornadic vortex signatures (TVSs), but the WSR-88Ds are limited to using predefined volume coverage patterns with an update interval of 4.5 min or longer. Such update times are insufficient to track the rapid evolution of TVSs that persist for only a few minutes. Additionally, more frequent volumetric updates are needed to detect and monitor the rapid evolution of radar-based signatures that may indicate tornadic development.

This study uses data from the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) to evaluate the impact of rapid sampling during two short-lived tornado events. In each event, volumetric updates were obtained with a maximum update time of 60 s; this scanning method provided frequent updates on the evolution of the observed circulations. On 19 August 2007, 45-s updates depicted the life cycle of a circulation associated with a tornado that formed between 0144 and 0147 UTC. Two minutes prior to tornado development, strong gate-to-gate shear of 40—50 m s-1 was found over a depth of 2 km, and this shear persisted through a 10-min period including the tornado lifetime. A second circulation was sampled on 07 May 2008, when a mesoscale convective vortex (MCV) developed in the vicinity of a surface cyclone. A tornado developed at the western edge of the MCV and remained on the ground through the period 2221—2226 UTC. Strong gate-to-gate shear in excess of 30 m s-1 was detected at 1.5 km AGL as early as 2217 UTC, providing indications that a strong circulation developed several minutes before the tornado reached the ground.

To examine the impact of sampling intervals on the evolution of these circulations, the original NWRT PAR data from both events are modified to produce temporal updates that are comparable with WSR-88D scanning strategies. Changes in gate-to-gate shear within the TVS are measured to compare the depiction and evolution of the tornadic vortex signatures. In addition, the positions of the TVSs are compared to evaluate the improvement that rapid sampling provides when tracking the location of a possible tornado.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper182379.html.

Sobash, R. A., D. R. Bright, A. R. Dean, J. S. Kain, M. C. Coniglio, S. J. Weiss, J. J. Levit, 2008: Severe storm forecast guidance based on explicit identification of convective phenomena in WRF-model forecasts. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 11.3.

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142187.htm.

Sobash, R. A., J. S. Kain, D. R. Bright, A. R. Dean, M. C. Coniglio, S. J. Weiss, J. J. Levit, 2009: Forecast guidance for severe thunderstorms based on identification of extreme phenomena in convection-allowing model forecasts. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Omaha, NE, USA, Amer. Meteor. Soc., CD-ROM, 4B.6.

Available online at http://ams.confex.com/ams/23WAF19NWP/techprogram/paper_154328.htm.

Stadler, S. J., P. Bothwell, A. Finchum, B. Battle, R. M. Rabin, E. Prins, 2008: Oklahoma Fire Geography: Atmosphere, Humans, and Vegetation.. Extended Abstracts, Association of American Geographers Annual Meeting, Boston, MA, USA, Association of American Geographers, 5223.2.

Stalker, S. L., K. M. Kuhlman, H. Lazrus, R. A. Peppler, K. E. Klockow, 2011: Public perceptions of the 10 May 2010 Oklahoma and the 17 June 2010 Minnesota tornado outbreaks. Extended Abstracts, Sixth Symposium on Policy and Socio-economic Research, Seattle, WA, USA, American Meteorological Society, J15.2.

The purpose of this project is to gather initial actions and reactions, from the public, in response to the 10 May 2010 Oklahoma and the 17 June 2010 Minnesota tornado outbreaks. This is done in support of the National Severe Storms Laboratory's Warn-on-Forecast project for severe thunderstorm, tornado, and flash flood events. The tools and products that will be developed as part of the project are needed to improve warning for both the public and community stakeholders i.e. emergency managers, hospitals, and schools. The first part of this research study consisted of formal interviews of 6 individuals impacted by the May 10 storm in Oklahoma and analysis of their responses. Preliminary results show that the majority of the interviewees did not feel any direct threat from the tornado during the early stages of storm development and advisories. Interestingly, with a longer lead-time promised by Warn-on-Forecast, most said they would still probably wait to obtain more information before taking any form of shelter or enact a safety plan. However, a majority of the participants believed it would be beneficial to see information on the expected track of the storm, which Warn-on-Forecast could provide, in order to help the individual make their own decisions on whether they felt the need to take safety measures. The results from interviews following the June 17 Minnesota outbreak will be used in comparison to the May 10 outbreak. Comparison of the two datasets will help distinguish regional differences, if any, in tornado perceptions. The results in this study are intended to aid the National Severe Storms Laboratory in further development of the Warn-on-Forecast system with respect to public perspectives on longer lead times and other information needs.

Stensrud, D. J., N. Yussouf, M. E. Baldwin, J. T. McQueen, J. Du, B. Zhou, B. Ferrier, G. Manikin, F. M. Ralph, J. M. Wilczak, A. B. White, I. Djlalova, J. W. Bao, R. J. Zamora, S. G. Benjamin, P. A. Miller, T. L. Smith, T. Smirnova, M. F. Barth, 2006: The New England High-Resolution Temperature Program. Bulletin of the American Meteorological Society, 87, 491-498.

The New England High-Resolution Temperature Program seeks to improve the accuracy of summertime 2-m temperature and dewpoint temperature forecasts in the New England region through a collaborative effort between the research and operational components of the National Oceanic and Atmospheric Administration (NOAA). The four main components of this program are 1) improved surface and boundary layer observations for model initialization, 2) special observations for the assessment and improvement of model physical process parameterization schemes, 3) using model forecast ensemble data to improve upon the operational forecasts for near surface variables, and 4) transfering knowledge gained to commercial weather services and end users. Since 2002 this program has enhanced surface temperature observations by adding 70 new automated Cooperative Observer Program (COOP) sites, identified and collected data from over 1000 non-NOAA mesonet sites, and deployed boundary layer profilers and other special instrumentation throughout the New England region to better observe the surface energy budget. Comparisons of these special data sets with numerical model forecasts indicate that near surface temperature errors are strongly correlated to errors in the model predicted radiation fields. The attenuation of solar radiation by aerosols is one potential source of the model radiation bias. However, even with these model errors, results from bias-corrected ensemble forecasts are more accurate than the operational model output statistics (MOS) forecasts for 2-m temperature and dewpoint temperature, while also providing reliable forecast probabilities. Discussions with commerical weather vendors and end users have emphasized the potential economic value of these probabilistic ensemble-generated forecasts.

Stensrud, D. J., M. Xue, L. J. Wicker, K. E. Kelleher, M. P. Foster, J. T. Schaefer, R. S. Schneider, S. G. Benjamin, S. S. Weygandt, J. T. Ferree, J. P. Tuell, 2009: Convective-scale warn on forecast: A vision for 2020. Bulletin of the American Meteorological Society, 90, 1487-1499.

The National Oceanic and Atmospheric Administration’s (NOAA’s) National Weather Service (NWS) issues warnings for severe thunderstorms, tornadoes, and flash floods since these phenomena are a threat to life and property. These warnings are presently based upon either visual confirmation of the phenomena or the observational detection of proxy signatures that are largely based upon radar observations. Convective-scale weather warnings are unique in the NWS by having little reliance on direct numerical forecast guidance. Since increasing severe thunderstorm, tornado, and flash flood warning lead times is a key NOAA strategic mission goal designed to reduce the loss of life, injury, and economic costs of these high impact weather phenomena, a new warning paradigm is needed in which numerical model forecasts play a larger role in convective-scale warnings. This new paradigm shifts the warning process from warn-on-detection to warn-on-forecast and has the potential to dramatically increase warning lead times.

A warn-on-forecast system is envisioned as a probabilistic convective-scale ensemble analysis and forecast system that assimilates in-storm observations into a high-resolution convection-resolving model ensemble. The building blocks needed for such a system are presently available and initial research results clearly illustrate the value of radar observations to the production of accurate analyses of convective weather systems and improved forecasts. While a number of scientific and cultural challenges still need to be overcome, the potential benefits are significant. A probabilistic convective-scale warn-on-forecast system is a vision worth pursuing.

Stensrud, D. J., J. Gao, T. M. Smith, K. L. Manross, J. Brogden, V. Lakshmanan, 2010: A realtime weather-adaptive 3DVAR analysis system with automatic storm positioning and on-demand capability. Preprints, 25th Conference on Severe Local Storms, Denver, CO, USA, AMS, CD-ROM, 8B.1.

Radar is a fundamental tool for severe storm monitoring and nowcasting activities. Forecasters examine real-time WSR-88D observations from multiple radars, other remote sensing tools, severe weather detection algorithms, and use their considerable experience and situational awareness to issue severe storm warnings that help protect the public from hazardous weather events. Escalating data flow rates from new sensors and applications, however, will make it challenging for forecasters to make the best use of all the available data in warning operations. In this study, we investigate the possibility of identifying supercells with a real-time, dynamically-adaptive three-dimensional variational data assimilation (3DVAR) system that incorporates all available radar observations. A storm positioning program is implemented in the 3DVAR system based on the National Severe Storm Laboratory (NSSL) WDSS-II two-dimensional composite reflectivity product. The system has the ability to automatically detect and analyze severe local hazardous weather by identifying mesocyclones at high spatial resolution (1km horizontal resolution) and high time frequency (every 5 minutes) using data primarily from the national WSR-88D radar network and NCEP's North American Mesoscale (NAM) model product. The analysis can also be performed with on-demand capability in which end-users (or forecasters) set up the location of the analysis domain in real time based on the current weather situation. Although still in the early development stage, this system performed very well during the spring of 2010. Many severe weather events, such as the Mississippi tornadoes on April 24th, Arkansas tornadoes on April 26th, and Oklahoma/Kansas tornadoes and hailstorms on May 10th, May 16th, May 19th, May 25th were all successfully detected and analyzed.

The objectivity of the procedure ensures that (i) all available information, including all nearby WSR-88Ds and NAM high resolution analysis and forecast products, are used, (ii) physically-consistent gridded data are provided to forecasters to help make their warning decisions in a timely manner, and (iii) the problem of subjectivity, inherent to some arbitrary criteria in some severe weather detection algorithms, is avoided. Furthermore, the analysis system can be also run offline, and this enables, for example, the study of a specific area in greater detail or the investigation of the evolution and lifetime of certain kinds of severe weather. The performance of the system will be accessed and discussed in the conference.

Straka, J., E. Mansell, D. MacGorman, E. Bruning, C. L. Ziegler, 2007: Comparison of modeled and observed electrical charging and lightning in a low-precipitation supercell storm during TELEX. Preprints, 13th International Conference on Atmospheric Electricity, Beijing, China, International Commission on Atmospheric Electricity, 272-275.

Stumpf, G. J., S. B. Smith, K. E. Kelleher, 2005: Collaborative activities of the NWS MDL and NSSL to improve and develop new severe weather warning guidance applications. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, P2.13.

Stumpf, G. J., K. D. Hondl, S. B. Smith, M. T. Filiaggi, V. Lakshmanan, 2005: Status on the four-dimensional base radar data analysis tool for AWIPS. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 8R.5.

Stumpf, G. J., M. T. Filiaggi, M. A. Magsig, K. D. Hondl, S. B. Smith, R. Toomey, C. Kerr, 2006: Status on the integration of the NSSL Four-dimensional Stormcell Investigator (FSI) into AWIPS. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, American Meteorological Society, CD-ROM, 8.3.

Stumpf, G. J., T. M. Smith, D. L. Andra, D. W. Burgess, J. G. LaDue, L. R. Lemon, M. A. Magsig, K. Manross, D. J. Miller, S. Nelson, K. L. Ortega, K. Scharfenberg, D. W. Sharp, 2008: Experimental gridded warning guidance for severe convective weather threats. Extended Abstracts, 24th Conf. on IIPS, New Orleans, LA, USA, Amer. Meteor. Soc., P1.3.

Suarez, A., H. D. Reeves, D. Wheatley, M. Coniglio, 2012: Comparison of Ensemble Kalman Filter–Based Forecasts to Traditional Ensemble and Deterministic Forecasts for a Case Study of Banded Snow. Weather and Forecasting, 27, 85-105.

The ensemble Kalman filter (EnKF) technique is compared to other modeling approaches for a case study of banded snow. The forecasts include a 12- and 3-km grid-spaced deterministic forecast (D12 and D3), a 12-km 30-member ensemble (E12), and a 12-km 30-member ensemble with EnKF-based four- dimensional data assimilation (EKF12). In D12 and D3, flow patterns are not ideal for banded snow, but they have similar precipitation accumulations in the correct location. The increased resolution did not improve the quantitative precipitation forecast. The E12 ensemble mean has a flow pattern favorable for banding and precipitation in the approximate correct location, although the magnitudes and probabilities of relevant features are quite low. Six members produced good forecasts of the flow patterns and the precipitation structure. The EKF12 ensemble mean has an ideal flow pattern for banded snow and the mean produces banded precipitation, but relevant features are about 100 km too far north. The EKF12 has a much lower spread than does E12, a consequence of their different initial conditions. Comparison of the initial ensemble means shows that EKF12 has a closed surface low and a region of high low- to midlevel humidity that are not present in E12. These features act in concert to produce a stronger ensemble-mean cyclonic system with heavier precipitation at the time of banding.

Available online at http://dx.doi.org/10.1175/WAF-D-11-00030.1.

Tabary, P., G. Vulpiani, J. J. Gourley, A. J. Illingworth, O. Bousquet, 2009: Unusually high differential attenuation at C-band: Results from a two-year analysis of the French Trappes polarimetric radar data. Journal of Applied Meteorology and Climatology, 48, 2037-2053.

Taylor, A. A., L. M. Leslie, D. J. Stensrud, 2005: Forecasts of near-surface variables using a coupled atmosphere-land surface model. 19th Conference on Hydrology, San Diego, CA, USA, American Meteorological Society, 1.6.

Teshiba, M., R. D. Palmer, P. B. Chilson, A. V. Ryzhkov, T. J. Schuur, 2005: Dynamics of Mesoscale Convective Systems Observed with a UHF Wind Profiler and a Polarimetric S-band Weather Radar. Extended Abstracts, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, JP3J.27.

Teshiba, M., P. Chilson, A. Ryzhkov, T. Schuur, L. Kanofsky, R. Palmer, 2007: Investigations of microphysical processes of rain formation using wind profilers and S-band polarimetric radar. Extended Abstracts, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, 8A.7.

Teshiba, M., P. B. Chilson, A. V. Ryzhkov, T. J. Schuur, R. D. Palmer, L. Kanofsky, 2007: Snow characteristics observed using two UHF wind profilers and a polarimetric S-band weather radar. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, American Meteorological Society, 8A.7.

Teshiba, M. S., P. B. Chilson, A. V. Ryzhkov, T. J. Schuur, R. D. Palmer, 2009: Investigation of microphysical processes of rain formation using UHF wind profilers and S-band polarimetric radar.. Journal of Atmospheric and Oceanic Technology, 26, 1940-1955.

Thigpen, J. F., S. Van Cooten, K. Monroe, L. Spence, R. H. Bacon, K. M. Patterson, D. Figursky, R. Bandy, J. Kelley, 2011: Improving a Classic Outreach Model by Integrating Researchers and Information-users: the Coastal and Inland Flood Observation and Warning Information System (CI-FLOW). Preprints, Sixth Symposium on Policy and Socio-Economic Research, Seattle, WA, USA, American Meteorological Society, 672.

Abstract Researchers and information users are typically in different institutional settings, each with different sets of communication skills, attitudes, knowledge, social systems and cultures. Drawing on work done in the 1960s (Berlo and others), the role of outreach and education in the scientific process is to help the “source” of information (researchers) reciprocally communicate with the “receiver” (information users) in an iterative process that results in satisfied users and better science. The key is to understand the context in which both the source and the receiver operate, then to design messages in ways that accurately transmit the information so that it can be easily understood and appreciated by the receiver . The CI-FLOW project uses a 21st century version of the model, which adds multiple feed-back loops and intermediary information “packagers” to allow “receivers” the ability to modify and improve message format and delivery. CI-FLOW is an inter-disciplinary multi-agency consortium focused on the mitigation of coastal hydrologic hazards in the Pamlico,Tar and Neuse River Basins of North Carolina. CI-FLOW is a unique program in that is coupling precipitation analysis and forecasts, river, wave, and storm surge modeling systems to provide more accurate total water predictions for estuarine rive systems. From its inception, the project has brought together weather and river forecasters, government and academic researchers, outreach specialists and the customers that will use CI-FLOW products to plan, design and test emerging and more effective methods to communicate inland and coastal flood forecast information. This paper how the modified model is being used to bring researchers and information users together to identify the most useful information elements and the best methods of displaying and transferring the information with cutting-edge technology.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Paper186560.html.

Thompson, W., S. Burk, J. Lewis, 2005: Fog and low clouds in a coastally trapped disturbance. J. Geophysical Research, 110, .

Thompson, W., S. Burk, J. Lewis, 2005: Fog and low clouds in a coastally trapped disturbance. Journal of Geophysical Research - D: Atmospheres, 110, .

Thompson, T. C., L. J. Wicker, M. Biggerstaff, D. Forsyth, 2009: EnKF Analysis of the 29 May 2004 Oklahoma City Supercell using Rapid-Scan Phased Array Radar Data. Preprints, Preprint, 5th European Conference on Severe Storms., Landshut, Germany, European Severe Storms Laboratory, ESSL, 116-117.

Available online at http://www.essl.org/ECSS/2009/preprints/O06-6-thompson.pdf.

Torres, S., I. Ivic, 2005: Demonstration of range oversampling techniques on the WSR-88D. Preprints, 32nd International Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, 4R.5.

Torres, S., 2005: Range and velocity ambiguity mitigation on the WSR-88D: Performance of the SZ-2 phase coding algorithm. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, 19.2.

Torres, S., M. Sachidananda, D. Zrnic, 2005: Signal Design and Processing Techniques for WSR-88D Ambiguity Resolution. Phase Coding and Staggered PRT 9, 112 pp. [Available from Sebastian Torres, National Severe Storms Laboratory, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Available online at http://cimms.ou.edu/rvamb/Documents/Report_9.pdf.

Torres, S., 2006: Range and velocity ambiguity mitigation on the WSR-88D: Performance of the staggered PRT algorithm. Extended Abstracts, 22nd International Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, AMS, CD-ROM, 9.9.

In the WSR-88D, the range and Doppler velocity ambiguity problems are coupled such that trying to alleviate one of them worsens the other. Accordingly, special techniques are necessary to resolve both ambiguities to the levels required for the efficient observation of severe weather. The Radar Operations Center of the National Weather Service has sponsored the National Severe Storms Laboratory (NSSL) and the National Center for Atmospheric Research (NCAR) to develop methods for mitigating the effects of velocity and range ambiguities on the WSR-88D. NSSL has recently recommended an algorithm for the second stage of deployment of range and velocity ambiguity mitigation techniques on the Open Radar Data Acquisition (ORDA) subsystem. The algorithm is based on alternating pulse repetition times (PRT) and can replace the Batch cuts at intermediate elevation angles of the antenna beam. This paper shows the performance of the staggered PRT algorithm on weather data collected with NSSL's KOUN radar in Norman, OK. Comparisons with existing “legacy” algorithms demonstrate the ability of the staggered PRT algorithm to effectively mitigate range and velocity ambiguities in future enhancements of the NEXRAD radar network.

Available online at http://cimms.ou.edu/rvamb/Documents/AMS_IIPS_2006.pdf.

Torres, S. M., W. J. Gonzalez-Espada, 2006: Calculating 'g' from acoustic Doppler data. The Physics Teacher, 44, 536-539.

Torres, S. M., C. D. Curtis, 2007: Initial implementation of super-resolution data on the NEXRAD network. Preprints, 23rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, AMS, CD-ROM, 5B.10.

Torres, S. M., C. D. Curtis, 2006: Design considerations for improved tornado detection using super-resolution data on the NEXRAD network. Preprints, 4th European Conf. on Radar Meteorology and Hydrology (ERAD), Barcelona, Spain, Copernicus, 2.8.

Torres, S. M., D. S. Zrnic, 2006: Signal Design and Processing Techniques for WSR-88D Ambiguity Resolution. Evolution of the SZ-2 Algorithm 10, 74 pp.

Available online at http://cimms.ou.edu/rvamb/Documents/Report_10.pdf.

Torres, S. M., C. D. Curtis, D. S. Zrnic, M. Jain, 2007: Analysis of the new NEXRAD spectrum width estimator. Proc. 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P7.8.

Recently, the US network of weather surveillance radars (NEXRAD) was upgraded with new receiver, signal processor, and control subsystems. Before this upgrade, the spectrum width was estimated using the standard pulse-pair technique. The new signal processor implements a similar spectrum width estimator, but relies on a DFT-based estimator to compute the first few lags of the time-series autocorrelation function. Initial evaluation of the upgraded system demonstrated that, if combined with a tapered data window, the DFT-based estimator produces results that are acceptable and very close to the classical pulse-pair estimator. However, this paper demonstrates that, in general, the new and legacy autocorrelation estimators are not equivalent, resulting in inconsistent spectrum width estimates. Theoretical, simulation, and data analyses show that the new spectrum width estimator on non-windowed data is positively biased, especially for narrow spectrum widths. Given that biased estimates would negatively impact the performance of algorithms that rely on the spectrum width (e.g., the radar echo classifier, or the new turbulence detection algorithm), we propose changes to the new spectrum width estimator to make it unbiased, mathematically equivalent to the pulse-pair implementation, and naturally able to handle data window effects.

Available online at http://ams.confex.com/ams/pdfpapers/123048.pdf.

Torres, S. M., 2007: Range oversampling techniques for polarimetric radars with dual transmitters. Proc. AMS, Cairns, Australia, AMS, CD-ROM, 7.5.

Range oversampling followed by a decorrelation transformation is a novel method for increasing the number of independent samples from which to estimate the Doppler spectrum, its moments, as well as several polarimetric variables on pulsed weather radars. Range oversampling techniques rely on the precise knowledge of the range correlation of oversampled signals, which is a function of the transmitter pulse envelope, the receiver filter impulse response, and the reflectivity field illuminated by the radar. Theoretical and simulation studies demonstrating the advantages of these techniques have been successfully verified on weather data collected with a single-transmitter dual-polarization radar. In contrast, recent experimental results on a dual-transmitter system have been rather negative; if the amplitude and/or phase mismatch between transmission pulses is disregarded in the formulation of the decorrelation transformation, processing of range oversampled dual-polarization signals with the standard whitening transformation can produce biased polarimetric variable estimates. This paper demonstrates that, by properly accounting for the amplitude and/or phase differences in the transmission channels, it is always possible to obtain unbiased polarimetric variable estimates. However, the accuracy of these estimators degrades as the degree of mismatch between the horizontally and the vertically polarized transmitted pulses increases.

Available online at http://ams.confex.com/ams/pdfpapers/123045.pdf.

Torres, S. M., S. Bachmann, D. Zrnic, 2007: Signal Design and Processing Techniques for WSR-88D Ambiguity Resolution. Staggered PRT and Updates to the SZ-2 Algorithm 11, 146 pp.

Torres, S. M., C. Curtis, I. Ivic, S. Bachmann, E. Forren, J. Thompson, D. Priegnitz, R. Adams, A. Zahrai, 2008: Signal Processing Upgrades for the National Weather Radar Testbed. Preprints, 24rd International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, AMS, CD-ROM, 9A.2.

The National Weather Radar Testbed (NWRT) located in Norman, Oklahoma was established to demonstrate the potential to simultaneously perform aircraft tracking, wind profiling, and weather surveillance as a multi-mission phased-array radar (MPAR). Since its inception in September of 2003, the system has undergone an extensive engineering evaluation and numerous hardware and software upgrades. However, in spite of significant engineering work, the real-time signal processing functionality currently implemented in the PAR is limited. Even with these limitations, several research experiments have successfully demonstrated many of the unique advantages of using phase-array technology in the context of weather observation. A modern and improved multi-processor/multi-computer signal processing environment will allow the implementation of new and advanced real-time signal processing techniques. These include schemes to effectively remove clutter contamination from meteorological signals, methods to mitigate range and velocity ambiguities, and techniques that allow for faster data collection. This paper presents initial results and describes the roadmap of planned signal processing upgrades for the NWRT that will provide researchers and users with an optimum platform for demonstrating and evaluating the MPAR concept.

Torres, S., D. Zittel, D. Saxion, 2009: Update on Development of Staggered PRT for the NEXRAD Network. Preprints, 25th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, 11B.2.

Torres, S., C. Curtis, I. Ivic, D. Warde, E. Forren, J. Thompson, R. Adams, D. Priegnitz, 2009: Update on signal processing upgrades for the National Weather Radar Testbed. Preprints, 25th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, 8B.4.

Torres, S., 2008: Range and Velocity Ambiguity Mitigation on the US NEXRAD Network: Performance and Improvements of the SZ-2 Phase Coding Algorithm. Preprints, Fourth European Conf. on Radar Meteorology and Hydrology (ERAD), Helsinki, Finland, Finnish Meteorological Institute, CD-ROM, P9.10.

Torres, S., R. Passarelli, A. Siggia, P. Karhunen, 2008: Alternating Dual-Pulse, Dual-Frequency Techniques for Range and Velocity Ambiguity Mitigation on Weather Radars. Preprints, Fourth European Conf. on Radar Meteorology and Hydrology (ERAD), Helsinki, Finland, Finnish Meteorological Institute, CD-ROM, P9.6.

Torres, S., P. Heinselman, 2009: Super resolution for the NEXRAD network. National Weather Association Newsletter, 1, 2-2.

Available online at http://www.nwas.org/newsletters/pdf/news_jan2009.pdf.

Torres, S., D. Zrnic, 2009: Generalized SZ phase codes to mitigate range and velocity ambiguities. Extended Abstracts, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P5.10.

Torres, S., 2009: Whitening of oversampled signals in range on polarimetric weather radars with mismatched channels. Journal of Atmospheric and Oceanic Technology, 26, .

Processing oversampled signals in range with a whitening transformation has been proposed as a means to reduce the variance of meteorological variable estimates on polarimetric Doppler weather radars. However, the original formulation to construct decorrelation transformations does not account for mismatches in the polarimetric channels, which results in abnormally biased polarimetric variable estimates if the two channels are not perfectly matched. This paper extends the initial formulation and demonstrates that, by properly accounting for the differences in the polarimetric channels, it is always possible to produce optimum estimates of all meteorological variables. Simulation analyses based on the reported characteristics of existing polarimetric radars are included to illustrate the performance of the proposed transformations.

Torres, S., D. Warde, D. Zrnic, 2010: Signal Design and Processing Techniques for WSR-88D Ambiguity Resolution. Staggered PRT Updates 13, 142 pp.

Torres, S., D. Warde, D. Zrnic, 2009: Signal Design and Processing Techniques for WSR-88D Ambiguity Resolution. Staggered PRT Updates and Generalized Phase Codes 12, 156 pp.

Torres, S., 2009: Processing of Oversampled Signals in Range on Polarimetric Weather Radars with Mismatched Channels. Journal of Atmospheric and Oceanic Technology, 26, 1289-1301.

Processing oversampled signals in range with a whitening transformation has been proposed as a means to reduce the variance of meteorological variable estimates on polarimetric Doppler weather radars. However, the original formulation to construct decorrelation transformations does not account for mismatches in the polarimetric channels, which results in abnormally biased polarimetric variable estimates if the two channels are not perfectly matched. This paper extends the initial formulation and demonstrates that, by properly accounting for the differences in the polarimetric channels, it is always possible to produce optimum estimates of all meteorological variables. Simulation analyses based on the reported characteristics of existing polarimetric radars are included to illustrate the performance of the proposed transformations.

Available online at http://journals.ametsoc.org/doi/pdf/10.1175/2009JTECHA1209.1.

Torres, S., C. Curtis, I. Ivic, D. Warde, E. Forren, J. Thompson, D. Priegnitz, R. Adams, 2010: Update on signal processing upgrades for the National Weather Radar Testbed. Preprints, 26th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 14B.2.

Torres, S. M., P. Heinselman, 2010: Multifunction phased-array radar for weather surveillance. Preprints, 6th European Conf. on Radar in Meteorology and Hydrology: Adv. in Radar Technology, Sibiu, Romania, National Meteorological Administration, Romania, 52-58.

Torres, S., R. Passarelli, A. Siggia, P. Karhunen, 2010: Alternating dual‐pulse, dual‐frequency techniques for range and velocity ambiguity mitigation on weather radars. Journal of Atmospheric and Oceanic Technology, 27, 1461-1475.

Torres, S. M., R. Adams, C. Curtis, E. Forren, I. Ivic, D. Priegnitz, J. Thompson, D. Warde, 2011: Software and signal processing upgrades for the National Weather Radar Testbed phased-array radar. Extended Abstracts, 27th Conference on Interactive Information and Processing Systems (IIPS), Seattle, WA, USA, Amer. Meteor. Soc., 12B.3.

Available online at http://ams.confex.com/ams/91Annual/webprogram/Manuscript/Paper183394/IIPS%202011.pdf.

Torres, S., P. Heinselman, R. Adams, C. Curtis, E. Forren, I. Ivic, D. Priegnitz, J. Thompson, D. Warde, 2012: ADAPTS Implementation: Can we exploit phased-array radar's electronic beam steering capabilities to reduce update times?. Extended Abstracts, 28th Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, USA, Amer. Meteor. Soc., 6B.3.

It is well understood that high-temporal resolution data has the potential to improve the understanding, detection, and warning of hazardous weather phenomena. In fact, in a 2008 survey about scanning strategy improvements conducted by the US National Weather Service, 62% of forecasters indicated the need for faster updates. One of the strongest advantages of using phased-array radars for weather observations is their potential to produce data with very high temporal resolution. Naturally, this has been a major research and development thrust on the National Severe Storms Lab’s (NSSL) National Weather Radar Testbed Phased-Array Radar (NWRT PAR).
One way to get faster updates without loss in data quality is by adaptively focusing observations to the regions of interest. This is the purpose of the Adaptive DSP Algorithm for Timely Scans (ADAPTS), which was first demonstrated in 2009. ADAPTS works by activating or deactivating individual beam positions within a scanning strategy based on elevation, significance, and neighborhood criteria. Preliminary evaluations of ADAPTS showed significant time savings, but also helped identify areas for further improvement. This paper describes the initial implementation of ADAPTS, its recent evolution, and outlines a plan for future enhancements towards obtaining the best weather observations in the shortest amount of time.

Torres, S., C. Curtis, 2011: A fresh look at the range weighting function for modern weather radars. Extended Abstracts, 35th Conf. on Radar Meteor., Pittsburgh, PA, USA, Amer. Meteor. Soc., CD-ROM, 16B.1.

The range weighting function (RWF) is normally introduced in discussions of the radar resolution volume because it defines the radial extent of such volumes. The RWF determines how individual scatterer contributions are weighted as a function of range to produce estimates of the meteorological variables associated with a single resolution volume. The RWF is commonly defined in terms of the transmitter pulse envelope and the receiver filter impulse response and determines the range resolution of a radar. Digital signal processing of echo samples along the range-time dimension (herein referred to as range-time processing) can also modify the effective RWF. This third contributor to the RWF has become more significant as novel range-time processing techniques (e.g., those that operate on range oversampled signals) have become feasible for real-time implementation on modern radar systems. The impact of range-time processing on the RWF is the focus of this paper. The effects of different types of range-time processing on the RWF are examined using typical processing schemes.
The relationship between the RWF and range resolution has already been mentioned, but the RWF is important for several other reasons. Reflectivity gradients can cause biases in reflectivity estimates and can also shift the range location assigned to these data (Mueller 1977; Johnston et al. 2002). Additionally, the combination of the RWF and the resolution volume spacing determines the correlation between meteorological data in range. This range correlation affects the variance reduction when meteorological-variable estimates are averaged along range to gain data precision at the cost of reduced range resolution. Finally, the RWF can also affect the performance of algorithms that process meteorological data. For example, changes in the effective resolution volume in angular and/or range extents can affect tornado detection algorithms that utilize Doppler velocity signatures (Wood and Brown 1997; Torres and Curtis 2006). These effects can be further complicated by the fact that some range-time processing techniques produce a different RWF at each resolution volume. An example is adaptive pseudowhitening; it uses a different linear transformation based on measurements of signal characteristics (e.g., signal-to-noise ratio and spectrum width) at every resolution volume (Curtis and Torres 2011). Because of these significant effects, it is important to understand how range-time processing affects the RWF.
In this paper, we compute the RWF arising from the processing of echo samples along the range-time dimension. It uses two elements: (1) a pulse matrix which is based on the transmitter pulse envelope and the receiver filter and (2) a transformation matrix which is determined by the type of range-time processing, thus capturing all three major contributors to the RWF: transmitter pulse envelope, receiver filter, and range-time processing.

Tromble, E., R. Kolar, K. Dresback, Y. Hong, B. Vieux, R. Luettich, K. Kelleher, S. Van Cooten, J. Gourley, 2010: Aspects of Coupled Hydrologic-Hydrodynamic Modeling for Coastal Flood Inundation. Proc. 11th International Conference on Estuarine and Coastal Modeling, Seatlle, WA, USA, American Society of Civil Engineers, 724-744.

The hydrodynamic model ADCIRC has been used extensively to model hurricane storm surge inundation. ADCIRC utilizes an unstructured triangular mesh that allows sufficient resolution of important features and has been coupled to STWAVE or SWAN to account for wind waves. However, river inflows applied to ADCIRC are usually constant values representative of flow rates during landfall. This may be adequate for systems producing flooding dominated by storm surge, but some systems cause significant precipitation-induced flooding as as surge, e.g., Hurricane Floyd produced only 3 meters of storm surge, but precipitation resulted in over 500-year flood levels on the lower Tar River. Current NOAA and DHS projects seek to produce holistic coastal flood inundation modeling by coupling hydrologic models, HL-RDHM and Vflo, to ADCIRC. Results from an idealized study show routing using a dynamic wave approximation for the momentum equation is necessary to accurately handle backwater effects; kinematic wave approximation routing should only be used upstream of backwater effects. The initial target area is the Tar and Neuse River region of coastal North Carolina. Preliminary application of ADCIRC, to a domain that includes major rivers in this area subject to backwater effects, forced with a discharge hydrograph at the upstream boundary produces promising results.

Available online at http://dx.doi.org/10.1061/41121(388)42.

Van Cooten, S., K. Elmore, D. Barbe, J. A. McCorquodale, D. Reed, 2009: A Statistical Methodology to Discover Precipitation Micro-Climates in Southeast Louisiana: Implications for Coastal Watersheds. Journal of Hydrometeorology, 11, .

Van Cooten, S., K. L. Elmore, David. E. Barb, J. A. McCorquodale, D. J. Reed, 2009: A Statistical Methodology to Discover Precipitation Microclimates in Southeast Louisiana: Implications for Coastal Watersheds. J. Hydrometeorol., 10, 1184-1202.

This study quantifies the spatial distribution of precipitation patterns on an annual basis for southeast Louisiana. To compile a long-term record of 24-h rainfall, rainfall reports collected by National Weather Service (NWS) cooperative observers were gathered from National Climatic Data Center (NCDC) archives, private collections of observational data held at regional and local libraries, NWS offices, and local utility providers. The reports were placed into a digital database in which each station’s record was subjected to an extensive quality control process. This process produced a database of daily rainfall reports for 59 south Louisiana stations for the period 1836–2002, with extensive documentation for each site outlining the differences between the study’s data and the data available from the NCDC Web page. A statistical methodology was developed to determine if the four NCDC climate divisions for southeast Louisiana accurately depict average monthly rainfall for the area. This method employs cluster analysis, using Euclidean distance as the measure of dissimilarity for the clustering technique. To resolve missing rainfall observations, an imputation scheme was developed that uses the two most similar stations (based on Euclidean distance) to determine appropriate values for missing rainfall observations. Results from this testing structure show statistical evidence of precipitation microclimates across south Louisiana at higher spatial scales than those of the NCDC climate zones. Quantifying the spatial extent of daily precipitation and documenting historical trends of precipitation provides critical design information for regional infrastructure within this highly vulnerable area of the central Gulf Coast region.

Van Cooten, S., K. E. Kelleher, K. W. Howard, J. Zhang, J. J. Gourley, J. S. Kain, K. Nemunaitis-Monroe, A. Arthur, C. Langston, Z. Flamig, H. Moser, . et al., 2011: The CI-FLOW Project: A System for Total Water Level Prediction from the Summit to the Sea. Bulletin of the American Meteorological Society, 92, 1427-1442.

The objective of the Coastal and Inland Flooding Observation and Warning (CI-FLOW) project is to prototype new hydrometeorologic techniques to address a critical NOAA service gap: routine total water level predictions for tidally influenced watersheds. Since February 2000, the project has focused on developing a coupled modeling system to accurately account for water at all locations in a coastal watershed by exchanging data between atmospheric, hydrologic, and hydrodynamic models. These simulations account for the quantity of water associated with waves, tides, storm surge, rivers, and rainfall, including interactions at the tidal/surge interface.

Within this project, CI-FLOW addresses the following goals: i) apply advanced weather and oceanographic monitoring and prediction techniques to the coastal environment; ii) prototype an automated hydrometeorologic data collection and prediction system; iii) facilitate interdisciplinary and multiorganizational collaborations; and iv) enhance techniques and technologies that improve actionable hydrologic/hydrodynamic information to reduce the impacts of coastal flooding. Results are presented for Hurricane Isabel (2003), Hurricane Earl (2010), and Tropical Storm Nicole (2010) for the Tar–Pamlico and Neuse River basins of North Carolina. This area was chosen, in part, because of the tremendous damage inflicted by Hurricanes Dennis and Floyd (1999). The vision is to transition CI-FLOW research findings and technologies to other U.S. coastal watersheds.

Available online at http://journals.ametsoc.org/doi/pdf/10.1175/2011BAMS3150.1.

Van Cooten, S., K. Kelleher, K. Howard, J. Zhang, J. J. Gourley, C. Langston, V. Farmer, K. Monroe, Z. L. Flamig, H. Moser, R. Kolar, Y. Hong, K. Dresback, E. Tromble, H. Vergara, R. Luettich, B. Blanton, K. Galuppi, C. A. Blain, J. F. Thigpen, K. Mosher, D. Figursky, M. Moneypenny, J. Orrock, R. Bandy, C. Goodall, J. Kelley, J. Greenlaw, M. Wengren, D. Eslinger, J. Payne, J. Feldt, J. Schmidt, T. Hamill, R. H. Bacon, R. Stickney, L. Spence, 2011: Coastal and Inland FLooding Observation and Warning (CI-FLOW) Project-An Assesment of Research Outcomes From An Integrated Hydrologic Prediction System for Coastal Watersheds. Preprints, 25th Conference on Hydrology, Seattle, WA, USA, American Meteorological Society, 7.4.

The objective of the Coastal and Inland FLooding Observation and Warning (CI-FLOW) project is to develop and prototype new hydrometeorological techniques to address a critical NOAA service gap: routine total water level predictions for tidally-influenced watersheds. Since February 2000, the project has focused on developing a system to accurately account for water at all locations in a coastal watershed. The CI-FLOW computing framework interactively exchanges data between atmospheric, river, and ocean models to produce water quantity simulations upstream and downstream of the tidal plain, including shorelines. These simulations account for the quantity of water associated with waves, tides, storm surge, rivers, and rainfall, inclusive of interactions at the tidal/surge interface.

Within this framework, CI-FLOW accomplishes the following goals: 1) apply advanced weather monitoring and prediction techniques to the coastal environment; 2) prototype an automated hydrometeorological data collection and prediction system; 3) facilitate interdisciplinary and multi-organizational collaborations; and 4) enhance techniques and technologies that improve actionable hydrologic information to reduce the impacts of coastal floods/flash floods. Results are presented for Hurricane Isabel, the first test of the integrated framework, for the Tar-Pamlico and Neuse river basins of North Carolina. This area was chosen, in part, because of the tremendous damage inflicted by Hurricanes Dennis and Floyd in September 1999. However, the vision is to transition CI-FLOW research findings and technologies to other U.S. coastal watersheds

Available online at http://ams.confex.com/ams/91Annual/flvgateway.cgi/id/17363?recordingid=17363.

Van Den Broeke, M. S., D. M. Schultz, R. H. Johns, J. S. Evans, J. E. Hales, 2005: Cloud-to-ground lightning production in strongly forced, low-instability convective lines associated with damaging wind. Weather and Forecasting, 20, 517-530.

Vasiloff, S. V., D. J. Seo, K. W. Howard, J. Zhang, D. H. Kitzmiller, M. G. Mullusky, W. F. Krajewski, E. A. Brandes, R. M. Rabin, D. S. Berkowitz, H. E. Brooks, J. A. McGinley, R. J. Kuligowski, B. G. Brown, 2007: Improving QPE and Very Short Term QPF: An Initiative for a Community-Wide Integrated Approach. Bulletin of the American Meteorological Society, 88, 1899-1911.

Accurate quantitative precipitation estimates (QPE) and very short term quantitative precipitation forecasts (VSTQPF) are critical to accurate monitoring and prediction of water-related hazards and water resources. While tremendous progress has been made in the last quarter-century in many areas of QPE and VSTQPF, significant gaps continue to exist in both knowledge and capabilities that are necessary to produce accurate high-resolution precipitation estimates at the national scale for a wide spectrum of users. Toward this goal, a national next-generation QPE and VSTQPF (Q2) workshop was held in Norman, Oklahoma, on 28–30 June 2005. Scientists, operational forecasters, water managers, and stakeholders from public and private sectors, including academia, presented and discussed a broad range of precipitation and forecasting topics and issues, and developed a list of science focus areas. To meet the nation's needs for the precipitation information effectively, the authors herein propose a community-wide integrated approach for precipitation information that fully capitalizes on recent advances in science and technology, and leverages the wide range of expertise and experience that exists in the research and operational communities. The concepts and recommendations from the workshop form the Q2 science plan and a suggested path to operations. Implementation of these concepts is expected to improve river forecasts and flood and flash flood watches and warnings, and to enhance various hydrologic and hydrometeorological services for a wide range of users and customers. In support of this initiative, the National Mosaic and Q2 (NMQ) system is being developed at the National Severe Storms Laboratory to serve as a community test bed for QPE and VSTQPF research and to facilitate the transition to operations of research applications. The NMQ system provides a real-time, around-the-clock data infusion and applications development and evaluation environment, and thus offers a community-wide platform for development and testing of advances in the focus areas.

Vasiloff, S. V., K. Howard, J. Zhang, 2009: Difficulties with Correcting Radar Rainfall Estimates Based on Rain Gauge Data: A Case Study of Severe Weather in Montana on 16–17 June 2007.. Weather and Forecasting, 24, 1334-1344.

Vera, C., J. Beaz, M. Douglas, C. Emmanuel, J. Marengo, J. Meitin, M. Nicolini, J. Nouges-Paegle, J. Paegle, O. Penalba, P. Salio, C. Saulo, M. A. Silva-Dias, P. Silva-Dias, E. Zipser, 2006: The South American Low-Level Jet Experiment. Bulletin of the American Meteorological Society, 87, 63-77.

Verbout, S. M., L. M. Leslie, H. E. Brooks, D. Schultz, D. Karoly, 2005: Tornado outbreaks associated with land-falling tropical cyclones in the Atlantic Basin. Preprints, 6th Conference on Coastal Atmospheric and Oceanic Prediction and Processes, San Diego, CA, USA, American Meteorological Society, CD-ROM, 7.1.

Available online at http://ams.confex.com/ams/Annual2005/techprogram/paper_84926.htm.

Verbout, S. M., H. E. Brooks, L. M. Leslie, D. M. Schultz, 2006: Evolution of the U.S. tornado database: 1954-2004. Weather and Forecasting, 21, 86-93.

Over the last 50 yr, the number of tornadoes reported in the United States has doubled from about 600 per year in the 1950s to around 1200 in the 2000s. This doubling is likely not related to meteorological causes alone. To account for this increase a simple least squares linear regression was fitted to the annual number of tornado reports. A "big tornado day" is a single day when numerous tornadoes and/or many tornadoes exceeding a specified intensity threshold were reported anywhere in the country. By defining a big tornado day without considering the spatial distribution of the tornadoes, a big tornado day differs from previous definitions of outbreaks. To address the increase in the number of reports, the number of reports is compared to the expected number of reports in a year based on linear regression. In addition, the F1 and greater Fujita-scale record was used in determining a big tornado day because the F1 and greater series was more stationary over time as opposed to the F2 and greater series. Thresholds were applied to the data to determine the number and intensities of the tornadoes needed to be considered a big tornado day. Possible threshold values included fractions of the annual expected value associated with the linear regression and fixed numbers for the intensity criterion. Threshold values of 1.5% of the expected annual total number of tornadoes and/or at least 8 F1 and greater tornadoes identified about 18.1 big tornado days per year. Higher thresholds such as 2.5% and/or at least 15 F1 and greater tornadoes showed similar characteristics, yet identified approximately 6.2 big tornado days per year. Finally, probability distribution curves generated using kernel density estimation revealed that big tornado days were more likely to occur slightly earlier in the year and have a narrower distribution than any given tornado day.

Available online at http://www.cimms.ou.edu/~schultz/pubs/verboutetal06.pdf.

Verbout, S. M., D. M. Schultz, L. M. Leslie, H. E. Brooks, D. J. Karoly, K. L. Elmore, 2007: Tornado outbreaks associated with landfalling hurricanes in the north Atlantic Basin: 1954–2004. Meteorology and Atmospheric Physics, 97, 255-271.

Tornadoes are a notable potential hazard associated with landfalling hurricanes. The purpose of this paper is to discriminate hurricanes that produce numerous tornadoes (tornado outbreaks) from those that do not (nonoutbreaks). The data consists of all hurricane landfalls that affected the United States from the North Atlantic basin from 1954 to 2004 and the United States tornado record over the same period. Because of the more than twofold increase in the number of reported tornadoes over these 51 years, a simple least-squares linear regression ("the expected number of tornadoes") was fit to the annual number of tornado reports to represent a baseline for comparison.

The hurricanes were sorted into three categories. The first category, outbreak hurricanes, was determined by hurricanes associated with the number of tornado reports exceeding a threshold of 1.5% of the annual expected number of tornadoes and at least 8 F1 and greater tornadoes during the time of landfall (from outer rainbands reaching shore to dissipation of the system). Eighteen hurricane landfalls were classified as outbreak hurricanes. Second, 37 hurricanes having less han 0.5% of the annual expected number of tornadoes were classified as nonoutbreak landfalls. Finally, 28 hurricanes that were neither outbreak nor nonoutbreak hurricanes were classified as midclass hurricane landfalls.

Stronger hurricanes are more likely to produce tornado outbreaks than weaker hurricanes. While 78% of outbreak hurricanes were category 2 or greater at landfall, only 32% of nonoutbreak hurricanes were category 2 or greater at landfall. Hurricanes that made landfall along the southern coast of the United States and recurved northeastward were more likely to produce tornadoes than those that made landfall along the east coast or those that made landfall along the southern coast but did not recurve. Recurvature was associated with a 500-hPa trough in the jet stream, which also contributed to increased deep-layer shear through the hurricane, favoring mesocyclogenesis, and increased the low-level shear, favoring tornadogenesis. The origin of the hurricane, date of landfall, and El Niño-Southern Oscillation phase do not appear to be factors in outbreak hurricane creation. The results of this study help clarify inconsistencies in the previous literature regarding tornado occurrences in landfalling hurricanes.

Available online at http://www.springerlink.com/content/8132257282886516/fulltext.pdf.

Visco, T., V. Lakshmanan, T. M. Smith, K. L. Ortega, 2010: Diagnosis of azimuthal shear associated with tornadoes. Preprints, 26th Conference on Interactive Information Processing Systems, Atlanta, GA, USA, American Meteorological Society, 393.

Current rotation detection algorithms are prone to poor performance due to high local variance in a Doppler radial velocity field. A new linear least squares derivatives (LLSD) technique has been developed which is less prone to problems from such variability and outputs a number of fields diagnosing the radial wind field, including azimuthal shear and radial convergence. We subjectively diagnosed rotation within thunderstorms from seven storm days which yielded eighty tornadoes. Threshold values and trends of azimuthal shear and radial convergence fields were extracted from the tornado producing storms. These values and trends will be used to train a new rotation-detection algorithm.

Available online at http://ams.confex.com/ams/90annual/techprogram/paper_160516.htm.

Wandishin, M. S., M. E. Baldwin, S. L. Mullen, J. V. Cortinas, 2005: Short-range ensemble forecasts of precipitation type. Weather and Forecasting, 20, 609-626.

Wandishin, M. S., D. J. Stensrud, S. L. Mullen, L. J. Wicker, 2008: On the Predictability of Mesoscale Convective Systems: Two-Dimensional Simulations. Weather and Forecasting, 23, 773-785.

Mesoscale convective systems (MCSs) are a dominant climatological feature of the central United States and are responsible for a substantial fraction of warm season rainfall. Yet very little is known about the predictability of MCSs. To help alleviate this situation, a series of ensemble simulations of an MCS are performed on a two-dimensional, storm-scale (dx ~ 1 km) model. Ensemble member perturbations in wind speed, relative humidity, and instability are based on current 24-h forecast errors from the North American
Model (NAM). The ensemble results thus provide an upper bound on the predictability of mesoscale convective systems within realistic estimates of environmental uncertainty, assuming successful convective initiation.

The simulations are assessed by considering an ensemble member a success when it reproduces a convective system of at least 20 km in length (roughly the size of two convective cells) within 100 km on either side of the location of the MCS in the control run. By that standard, MCSs occur roughly 70% of the time for perturbation magnitudes consistent with 24-h forecast errors. Reducing the perturbations for all fields to one-half the 24-h error values increases the MCS success rate to over 90%. The same improvement in
forecast accuracy would lead to a 30%–40% reduction in maximum surface wind speed uncertainty and a roughly 20% reduction in the uncertainty in maximum updraft strength, and initially slower growth in the
uncertainty in the size of the MCS. However, the occurrence of MCSs drops below 50% as the midlayer mean relative humidity falls below 65%. The response of the model to reductions in forecast errors for instability, moisture, and wind speed is not consistent and cannot be easily generalized, but each can have a substantial impact on forecast uncertainty.

Wandishin, M. S., D. J. Stensrud, S. L. Mullen, L. J. Wicker, 2010: On the predictability of mesoscale convective systems: Three-dimensional simulations. Monthly Weather Review, 138, 863-885.

Mesoscale convective systems (MCSs) are a dominant climatological feature of the central United States and are responsible for a substantial fraction of warm-season rainfall. Yet very little is known about the predictability of MCSs. To help address this situation, a previous paper by the authors examined a series of ensemble MCS simulations using a two-dimensional version of a storm-scale (dx = 1 km) model. Ensemble member perturbations in the preconvective environment, namely, wind speed, relative humidity, and convective instability, are based on current 24-h forecast errors from the North American Model (NAM). That work is now extended using a full three-dimensional model.

Results from the three-dimensional simulations of the present study resemble those found in two dimensions. The model successfully produces an MCS within 100 km of the location of the control run in around 70% of the ensemble runs using perturbations to the preconvective environment consistent with 24-h forecast errors, while reducing the preconvective environment uncertainty to the level of current analysis errors improves the success rate to nearly 85%. This magnitude of improvement in forecasts of environmental conditions would represent a radical advance in numerical weather prediction. The maximum updraft and surface wind forecast uncertainties are of similar magnitude to their two-dimensional counterparts. However, unlike the two-dimensional simulations, in three dimensions, the improvement in the forecast uncertainty of storm features requires the reduction of preconvective environmental uncertainty for all perturbed variables. The MCSs in many of the runs resemble bow echoes, but surface winds associated with these solutions, and the perturbation profiles that produce them, are nearly indistinguishable from the nonbowing solutions, making any conclusions about the bowlike systems difficult.

Wang, B., J. Zhang, W. Xia, K. Howard, X. Xu, 2008: Analysis of radar and gauge rainfall during the warm season in Oklahoma. Preprints, The 22nd Conf. on Hydrology, New Orleans, LA, USA, Amer. Meteor. Soc., CD-ROM, P2.1.

Wang, J., Y. Hong, J. J. Gourley, P. Adhikari, L. Li, F. Su, 2010: Quantitative assessment of climate change and human impacts on long-term hydrologic response: a case study in a sub-basin of the Yellow River, China. International Journal of Climatology, 30, 2130-2137.

Wang, J., Y. Hong, L. Li, J. J. Gourley, S. I. Khan, K. K. Yilmaz, R. F. Adler, F. S. Policelli, S. Habib, D. Irwin, A. S. Limaye, T. Korme, L. Okello, 2011: The coupled routing and excess storage (CREST) distributed hydrological model. Hydrological Sciences Journal, 56, 84-98.

Wang, J., L. Li, H. Zhenchun, J. Gourley, 2011: Stream guiding algorithm for deriving flow direction from DEM and location of main streams. Vol. 346, Cold Regions Hydrology in a Changing Climate, International Association of Hydrologic Sciences Press, 208 pp.

The drainage paths and directions within the drainage basin are important for analyses of the interactions between human and nature. The stream burning algorithm is a popular D8-based method and can be effective in the digital reproduction of a known and generally accepted stream network. The stream guiding algorithm has been developed in this paper to overcome the stream burning algorithm’s disadvantage of locally altering elevation in order to provide the consistency between existing vector hydrography and the DEM. In the new algorithm, flow direction of LMS (location of main streams) grids will be determined first; then possible outlets in non-LMS area will be found; and finally, the flow direction of undetermined area will be calculated by a “filling up” technique. Evaluations for Taiwan Island show that the new algorithm has a similar performance to that of the stream burning algorithm in river network reproduction. The new algorithm obeys the “steepest decent rule” and DEM data more strictly than the stream burning algorithm, especially around the LMS grids.

Warde, D., S. Torres, 2009: Range Overlaid Staggered PRT. Preprints, 25th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, P2.2.

Warde, D. A., S. M. Torres, 2009: Automatic detection and removal of ground clutter contamination on weather radars. Preprints, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, CD-ROM, P10.11.

Radar backscatter from the ground can contaminate weather signals, often resulting in severely biased meteorological estimates. If not removed, these clutter returns tend to bias reflectivity high as well as Doppler velocity and spectrum width toward zero. A ground clutter filter (GCF) can mitigate this contamination and provide unbiased meteorological estimates but typically with reduced quality. Moreover, significant biases could occur if the GCF is applied when clutter is not present and the weather signal has near-zero Doppler velocities. Thus, the overall quality of the meteorological estimates needlessly suffers when a GCF is misapplied. The problem of applying the GCF becomes very complex, especially when considering the dynamic nature of the atmosphere. Anomalous propagation can cause the radar beam to increase contact or overshoot the clutter, giving the appearance that the clutter shifts within or disappears from the radar volume coverage very rapidly. In this dynamic environment, spectral examination of the received echoes provides a means to determine the presence of clutter in real time without having to rely on static clutter maps. However, spectral analysis on a finite number of samples suffers from spectral leakage. To combat spectral leakage, tapered windows are typically applied. Strong clutter returns may require the use of windows with high dynamic ranges, but the use of these windows reduces the quality and resolution of the meteorological estimates. On the other hand, weaker clutter returns may only require low dynamic range windows, which help preserve the quality and resolution of the meteorological estimates. Consequently, a ‘smart' filter is needed that can examine the received radar echoes, apply a tapered window that best suits the conditions, determine the exact number of spectral coefficients affected by clutter contamination, and, only then, apply the GCF.

In this paper, we introduce a spectral GCF capable of satisfying the aforementioned considerations. The filter is referred to as Clutter Environment ANalysis using Adaptive Processing (CLEAN-AP) and performs real-time detection and suppression of ground clutter returns in dynamic atmospheric environments. We characterize the statistical performance of the CLEAN-AP filter with simulated clutter/weather mix and show real weather examples.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_155681.htm.

Warde, D. A., S. M. Torres, 2009: The Range-Overlaid Staggered PRT Algorithm. Preprints, 34th International Conference on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, CD-ROM, P5.11.

A well-understood limitation of sampling the environment with weather radars is the Doppler dilemma. That is, if a uniform sampling period or pulse repetition time (PRT) is made large for extended range coverage, no overlaid conditions occur, but Doppler velocity measurements become ambiguously aliased. Conversely, if the PRT is made small to unambiguously resolve velocities, range-overlaid signals become more likely. The staggered PRT (SPRT) algorithm has been shown to mitigate range and velocity ambiguities by decreasing velocity aliasing while extending the radar coverage. However, the performance of the SPRT algorithm to accurately dealias Doppler velocities deteriorates as the spectrum width of the weather signal increases in relation to the Nyquist interval, an issue that is exacerbated for longer PRTs. In this work, we demonstrate that the SPRT algorithm can tolerate overlaid echoes better than with uniform sampling. By allowing some overlaid signals to occur, shorter PRTs can be used to increase the SPRT dealiasing performance. The reduced range coverage associated with the use of shorter PRTs is offset by providing a means to recover Doppler velocities and spectrum widths beyond the unambiguous range of the standard SPRT algorithm. This variation of the standard technique is referred to as the range-overlaid SPRT algorithm.

The performance of this novel technique is evaluated with simulations and real weather examples. The significant improvement with respect to more traditional signal processing techniques makes the range-overlaid SPRT algorithm a solid candidate to improve the mitigation of range and velocity ambiguities on operational weather radars.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_155685.htm.

Warde, D., S. Torres, 2010: A novel ground‐clutter‐contamination mitigation solution for the NEXRAD network: the CLEAN‐AP filter. Preprints, 26th International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 8.6.

Warde, D., S. Torres, 2010: Automated real-time mitigation of ground clutter contamination for Doppler weather radars. Preprints, 6th European Conf. on Radar in Meteorology and Hydrology: Adv. in Radar Technology, Sibiu, Romania, National Meteorological Administration, Romania, P2.10.

Warde, D., S. Torres, 2011: Spectral processing and ground clutter mitigation for dual polarization staggered PRT signals in Doppler weather radars. Extended Abstracts, 35th Conf. on Radar Meteor., Pittsburgh, PA, USA, Amer. Meteor. Soc., CD-ROM, 15B.1.

Ambiguities in range (out-of-trip echoes) and velocity (aliasing) arise in Doppler weather radars due to the large spatial extent and significant velocities associated with some weather conditions. Sirmans (1976) suggested that the staggered pulse repetition time (PRT) waveform could be used as a viable means to reduce range and velocity ambiguities. In the staggered PRT technique, two interlaced sampling rates are used to decrease (or eliminate) velocity aliasing while maintaining adequate range coverage at the expense of reducing the effectiveness of ground clutter filtering. For a while, the operational implementation of the staggered PRT algorithm had been prevented due to the inability to provide adequate ground clutter filter suppression. Sachidananda and Zrnic (2000) proposed a solution to this issue by introducing the Spectral Algorithm for Clutter Harmonics Identification (SACHI) which exploits spectral processing of samples from interlaced PRTs with a 2/3 ratio. More recently, Warde and Torres (2011) showed that the CLutter Environment Analysis using Adaptive Processing (CLEAN-AP) filter, described by the same authors in 2009, could be used not only to filter but to detect ground clutter contamination in staggered PRT waveforms with any PRT ratio. As Doppler weather radars are modernized to incorporate dual-polarization, future operational implementation of staggered PRT will require the computation of polarimetric variables. In this work, we present a dual-polarization staggered-PRT algorithm based on the framework provided in the CLEAN-AP filter which is valid for any staggered PRT ratio. The performance of the proposed algorithm is shown using simulations and archived WSR-88D data; these results confirm the suitability of this technique for future upgrades of the NEXRAD network.

Warde, D., S. Torres, 2011: Extending the CLEAN-AP filter to staggered PRT signals in Doppler weather radars. Extended Abstracts, 27th Conf. on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Seattle, WA, USA, Amer. Meteor. Soc., CD-ROM, 9.1.

The staggered pulse repetition time (PRT) algorithm has been shown to mitigate velocity and range ambiguities in Doppler weather radars by interlacing two sampling rates to decrease (or eliminate) velocity aliasing while maintaining adequate range coverage. However, the operational implementation of the staggered PRT algorithm still centers on providing adequate ground clutter filter suppression. Sachidananda and Zrnic (2000) proposed a solution to this issue by introducing the Spectral Algorithm for Clutter Harmonics Identification (SACHI) filter exploiting spectral processing using interlaced PRTs with a 2/3 ratio. In their approach, spectral analysis and clutter filtering are facilitated by the reconstruction of a uniformly sampled time sequence. Despite the effectiveness of this approach to filter ground clutter, it does not include the detection of ground clutter. Here, we present an alternative approach to spectral analysis and clutter mitigation (both detection and removal of ground clutter) for staggered PRT using autocorrelation spectral densities and the Clutter Environment Analysis using Adaptive Processing (CLEAN-AP) filter described by Warde and Torres (2009). Application and performance of this new algorithm is shown using simulations and recorded WSR-88D data. Comparisons to the SACHI filter are provided to gauge the filter performance of the new algorithm.
Here, the previous work is put in the context by establishing a complete scheduling framework that can be easily implemented for real-time operation on the NWRT PAR. The framework is modular and consists of four processes: (1) a storm identification algorithm, (2) a storm tracking algorithm, (3) a tasks configuration module, and (4) the TB scheduling algorithm. The storm identification algorithm automatically identifies 3D storm cells during the surveillance task so that updated information about the number, locations, and size of storm cells is provided to the tracking and TB algorithms. In this work, the same framework is used to simulate and evaluate the performance of the TB scheduling algorithm on multiple archived weather data cases. The performance of the TB scheduling algorithm can then be characterized by statistical analyses of the error between the theoretical and estimated quality measures. This is the 1st step towards a real-time implementation of the TB scheduling algorithm on the NWRT PAR, which will enable the demonstration of improvements that can be realized with focused, adaptive weather observations.

Weadon, M., P. Heinselman, D. Forsyth, W. Benner, G. Torok, J. Kimpel, 2009: Multifunction Phased Array Radar (MPAR). Bulletin of the American Meteorological Society, 90, 385-389.

Weiss, S., J. Kain, L. Wicker, R. Davies-Jones, D. Bright, J. Levit, G. Carbin, M. Baldwin, 2005: Evaluating the skill of daily explicit predictions of mesocyclones in multiple high-resolution WRF model forecasts during the 2005 SPC/NSSL Spring Program. Preprints, 12th Conf. On Mesoscale Processes,, Albuquerque, NM, USA, Amer. Meteor. Soc., no preprint.

Weiss, S. J., J. S. Kain, D. R. Bright, J. J. Levit, M. Pyle, Z. I. Janjic, B. Ferrier, J. Du, M. L. Weisman, M. Xue, 2007: The NOAA Hazardous Weather Testbed: Collaborative testing of ensemble and convection-allowing WRF models and subsequent transfer to operations at the Storm Prediction Center.. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 6B.4.

Weiss, S. J., J. S. Kain, D. R. Bright, J. J. Levit, M. Pyle, Z. I. Janjic, B. S. Ferrier, J. Du, M. L. Weisman, M. Xue, 2007: The NOAA Hazardous Weather Testbed: Collaborative testing of ensemble and convection-allowing WRF models and subsequent transfer to operations at the Storm Prediction Center. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, Amer. Mete. [Available from S. J. Weiss, SPC, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Since 2003, the Storm Prediction Center (SPC) has played a leading role in testing various configurations of Short-Range Ensemble Forecast (SREF) systems and high resolution WRF models for their operational utility. These test and evaluation activities have occurred during organized collaborative activities in the NOAA Hazardous Weather Testbed (HWT) in Norman. The HWT is designed to bring research scientists, model developers, and forecasters together to work on issues of mutual interest, facilitating the rapid transfer of research to operations. This organizational framework helps researchers and model developers to better understand the operational challenges and requirements of forecasters, educates forecasters on new science and technological advances, and has accelerated the application of new modeling approaches to severe weather forecasting. This paper focuses on the use of the operational NCEP SREF and two experimental high resolution convection-allowing WRF models as complementary sources of information for SPC forecasters.

NCEP is running a 21 member multi-model, multi-analysis SREF system with enhanced physics diversity four times daily with output through 87 hours. SPC processes the grids from all SREF members and produces a large variety of products for severe weather forecasting, including standard spaghetti, mean and spread, probability, and max/min charts, as well as specialized multi-parameter convective fields and post-processed calibrated probabilities for the occurrence of thunderstorms, dry thunderstorms, and severe thunderstorms.

NCEP has also been running an experimental high resolution WRF-Non-hydrostatic Mesoscale Model (WRF-NMM4) for the SPC since April 2004; this model was recently upgraded to a 4 km grid length. And starting in November 2006, SPC forecasters have had access to output from a 4 km Advanced Research WRF (WRF-ARW4) developed by NCAR and run at the National Severe Storms Laboratory. Both WRF models are initialized from a cold start once daily at 0000 UTC using initial and lateral boundary conditions from the operational North American Mesoscale model, and provide forecasts through a 36 hour period over a domain covering approximately three-fourths of the U.S. Several unique WRF products have been developed for use by severe weather forecasters, including simulated reflectivity and measures of updraft rotation in model-generated storms.

The incorporation of SREF and high resolution WRF guidance into an operational severe weather forecasting environment already dealing with high volumes of observational and model data requires careful assessment of the unique strengths of each modeling system, and knowledge of the specific needs of SPC forecasters. Since the SPC severe weather forecast mission focuses on phenomena smaller than that predicted by mesoscale models, such as tornadoes and severe thunderstorms, the traditional forecast methodology has focused on first predicting the evolution of the mesoscale environment and then determining the spectrum of convective storms a particular environment may support. SREF output has been found to be particularly useful in quantifying the likelihood that the environment will occupy specific parts of convective parameter space, as well as the likelihood and timing for thunderstorms and severe thunderstorms to develop over Outlook-scale regions. While this can be extremely helpful to SPC forecasters, more detailed information about the intensity and mode of storms is also needed, since the type of severe weather (e.g., tornadoes, damaging wind) is often strongly related to convective mode. The value of the high resolution WRF guidance is most evident here, as it has capability to resolve near storm-scale convective characteristics, such as the development of discrete cells ahead of a line of storms, and the development of model storms with rotating updrafts.

We will examine the complementary role of SREF and high resolution WRF output during several strongly-forced and weakly-forced severe weather days during the winter and spring severe weather period and illustrate the operational application of these model datasets in the SPC decision-making process for both Convective Outlooks and Watches.

Available online at http://ams.confex.com/ams/pdfpapers/124772.pdf.

Wen, Y., Y. Hong, G. Zhang, T. J. Schuur, J. J. Gourley, Z. Flamig, K. Morris, Q. Cao, 2011: Cross validation of spaceborne radar and ground polarimetric radar aided by polarimetric echo classification of hydrometeor types. Journal of Applied Meteorology and Climatology, 50, 1389-1402.

Willingham, K. M., E. J. Thompson, K. W. Howard, C. L. Dempsey, 2011: Characteristics of Sonoran Desert Microbursts. Weather and Forecasting, 26, 94-108.

During the 2008 North American monsoon season, 140 microburst events were identified in Phoenix, Arizona, and the surrounding Sonoran Desert. The Sonoran microbursts were studied and examined for their frequency and characteristics, as observed from data collected from three Doppler radars and electrical power infrastructure damage reports. Sonoran microburst events were wet microbursts, and occurred most frequently in the evening hours (19-21 MST). Stronger maximum differential velocities (20-25 m s-1) were observed more frequently in Sonoran microbursts than in many previously documented microbursts. Alignment of Doppler radar data to reports of wind-related damage to electrical power infrastructure in Phoenix allowed a comparison of microburst wind damage versus gust-front wind damage. For these damage reports, microburst winds caused more significant damage than gust-front winds.

Available online at http://journals.ametsoc.org/doi/abs/10.1175/2010WAF2222388.1.

Wilson, C. J., K. L. Ortega, V. Lakshmanan, 2009: Evaluating multi-radar, multi-sensor hail diagnosis with high resolution hail reports. Extended Abstracts, 25th Conference on Interactive Information Processing Systems for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, American Meteorological Society, P2.9.

Low resolution verification data, as available from the Storm Data database, has hindered the development and evaluation of high resolution hail algorithms as well as the assessment of hail forecasting techniques. Previous studies have highlighted the inadequacies and inaccuracies associated with this verification data. This study uses high resolution ground-truth hail verification data from the Severe Hazards Analysis and Verification Experiment (SHAVE) to evaluate gridded synthetic hail verification and different radar derived parameters used in predicting severe hail.

MESH is found to have limited skill as a synthetic verification tool due to a high probability of false detection and a wide distribution of MESH values for each reported hail size range. In addition, radar-derived parameters are found to provide little skill in the prediction of severe hail as the probability of false detection associated with these parameters leads to low skill scores. The predictive skill of these parameters is also found to decrease with time, limiting the lead time in which skillful prediction of severe surface hail fall is possible using radar derived parameters.

Available online at http://ams.confex.com/ams/89annual/techprogram/paper_146206.htm.

Witt, A., R. A. Brown, V. Lakshmanan, 2005: Real-time calculation of horizontal winds using multiple Doppler radars: A new WDSS-II module. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, Amer. Meteor. Soc., CD-ROM, P8R.7.

Wood, V. T., L. W. White, C. R. Alexander, R. L. Tanamachi, 2006: An analytical model of one- and two-celled vortices: Preliminary testing. Preprints, 23rd Conference on Severe Local Storms, St. Louis, MO, USA, American Meteorological Society, CD-ROM, P10.1.

Wulfmeyer, V., A. Behrendt, C. Kottmeier, U. Corsmeier, C. Barthlott, G. C. Craig, M. Hagen, D. Althausen, F. Aoshima, M. Arpagaus, H. S. Bauer, L. Bennett, A. Blyth, C. Brandau, C. Champollion, S. Crewell, G. Dick, P. DiGirolamo, M. Dorninger, Y. Dufournet, R. Eigenmann, R. Engelmann, C. Flamant, T. Foken, T. Gorgas, M. Grzeschik, J. Handwerker, C. Hauck, H. Hoeller, W. Junkermann, N. Kalthoff, C. Kiemle, S. Klink, M. Koenig, L. Krauss, C. N. Long, F. Madonna, S. Mobbs, B. Neiniger, S. Pal, G. Peters, G. Pigeon, E. Richard, M. W. Rotach, H. Russchenberg, T. Schwitalla, V. Smith, R. Steinacker, J. Trentmann, D. D. Turner, J. van Baelen, S. Vogt, H. Volkert, T. Weckwerth, H. Wernli, A. Wieser, M. Wirth, 2011: The convective and orographically induced precipitation study (COPS): The scientific strategy, the field phase, and first highlights.. Quarterly Journal of the Royal Meteorological Society, 137, 3-30.

Within the framework of the international field campaign COPS (Convective and Orographically-induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. This includes networks of in situ and remote-sensing systems such as the Global Positioning System as well as a synergy of multi-wavelength passive and active remote-sensing instruments such as advanced radar and lidar systems. The COPS field phase was performed from 01 June to 31 August 2007 in a low-mountain area in southwestern Germany/eastern France covering the Vosges mountains, the Rhine valley and the Black Forest mountains. The collected data set covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase until their decay. Eighteen Intensive Observation Periods with 37 operation days and eight additional Special Observation Periods were performed, providing a comprehensive data set covering different forcing conditions. In this article, an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS research provides new insight into key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of quantitative precipitation forecasting by the assimilation of new observations, and in the performance of ensembles of convection-permitting models in complex terrain.

Xu, Q., K. Nai, L. Wei, P. Zhang, L. Wang, H. Lu, Qingyun Zhao, 2005: Progress in doppler radar data assimilation. 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, JP1J7.

Xu, Q., T. Lei, S. Gao, 2007: Modal and non-modal symmetric perturbations. Part 2. Non-modal growths measured by total perturbation energy. Journal of the Atmospheric Sciences, 64, 1764-1781.

Xu, Q., K. Nai, L. Wei, H. Lu, P. Zhang, S. Liu, D. Parrish, 2007: Estimating radar wind observation error and NCEP WRF background wind error covariances from radar radial-velocity innovations. Extended Abstracts, 18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., 1B.3.

Available online at http://ams.confex.com/ams/pdfpapers/123419.pdf.

Xu, X., K. Howard, J. Zhang, 2008: An Automated Radar Technique for the Identification of Tropical Precipitation. Journal of Hydrometeorology, 9, 885-902.

Xu, Q., K. Nai, L. Wei, P. Zhang, Q. Zhao, P. Harasti, 2009: A real-time radar wind data quality control and analysis system for nowcast application. Extended Abstracts, International Symposium on Nowcasting and Very Short Range Forecasting (WSN09), Whistler, Canada, WMO, CD-ROM, 3.5.

A real-time radar wind analysis system has been developed for monitoring low-level wind conditions at high spatial and temporal resolution. By ingesting real-time wind observations from KTLX radar, Oklahoma Mesonet data and NOAA Profiler Network, this system produces and displays real-time vector wind field at each selected vertical level or on each conical surface of radar scans superimposed on radar reflectivity or radial-velocity image. The products are made available to NWS Norman Forecast Office. The early system has been evaluated and used to provide real-time winds to drive high-resolution emergency response dispersion models. The key technical elements developed in the system for the radar data quality control and wind analysis are presented with illustrative examples.

Xu, Q., K. Nai, P. Zhang, S. Liu, D. Parrish, 2009: A new dealiasing method for Doppler velocity data quality control. Preprints, 34rd Conference on Radar Meteorology, Williamsburg, VA, USA, Amer. Meteor. Soc., CD-ROM, P9.6.

Available online at http://ams.confex.com/ams/34Radar/techprogram/paper_155947.htm.

Xu, Q., K. Nai, L. Wei, P. Zhang, S. Liu, D. Parrish, 2011: A VAD-based dealiasing method for radar velocity data quality control. Journal of Atmospheric and Oceanic Technology, 28, 50-62.

This paper describes a new VAD-based dealiasing method developed for automated radar radial-velocity data quality control to satisfy the high quality standard and efficiency required by operational radar data assimilation. The method is built on an alias-robust velocity azimuth display (AR-VAD) analysis. It upgrades and simplifies the previous three-step dealiasing method in three major aspects. First, the AR-VAD is used with sufficiently stringent threshold conditions in place of the original modified VAD for the preliminary reference check to produce alias-free seed data in the first step. Second, the AR-VAD is more accurate than the traditional VAD for the refined reference check in the original second step, so the original second step becomes unnecessary and is removed. Third, a block-to-point continuity check procedure is developed, in place of the point-to-point continuity check in the original third step, to enhance the use of available seed data in a properly enlarged block area around each flagged data point that is being checked with multiple threshold conditions to avoid false dealiasing. The new method has been tested extensively with aliased radial-velocity data collected under various weather conditions, including hurricane high-wind conditions. The robustness of the new method is exemplified by the result tested with a hurricane case. The limitations of the new method and possible improvements are discussed.

Xue, M., F. Kong, D. Weber, K. W. Thomas, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. S. Wandishin, M. C. Coniglio, J. Du, 2007: CAPS realtime storm-scale ensemble and high-resolution forecasts as part of the NOAA Hazardous Weather Testbed 2007 Spring Experiment.. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.1.

Xue, M., F. Kong, D. B. Weber, K. W. Thomas, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. S. Wandishin, M. C. Coniglio, J. Du, 2007: CAPS realtime storm-scale ensemble and high-resolution forecasts as part of the NOAA Hazardous Weather Testbed 2007 Spring Experiment. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.1. [Available from Ming Xue, CAPS, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

As a continuation of past collaborations with the NOAA Hazardous Weather Testbed (HWT), the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma will produce daily 10-member 4-km-resolution ensemble forecasts during the spring of 2007, as contributions to the HWT 2007 Spring Experiment. At the same time, a single 2-km deterministic forecast will be produced over the same domain that covers two thirds of the continental US. The forecasts will start from 2100 UTC and extend to 0600 UTC of the third day for a total length of 33 hours. The experiment will start in mid-April and last for about 2 months.

The CAPS effort in 2007 will use the WRF ARW model and the ensemble will include both initial/boundary condition and physics perturbations. The initial and boundary condition perturbations will come from the NCEP 2100 UTC SREF forecast cycle, with the control-member initial condition coming from the NAM 2100 UTC analysis on the 12 km grid. The physics perturbation members are designed for easy identification of the strengths and weakness of leading microphysics and PBL schemes within WRF.

Selected data fields will be fed directly into the NAWIPS systems in the HWT for use by experimental forecast and evaluation teams in the Spring Experiment. These will be combined with separate deterministic WRF forecasts at 3 km grid spacing, contributed by NCAR and EMC. Additional data fields from the CAPS runs will be posted on the web in realtime for external verification purposes. These include side by side comparisons of 2-km forecast composite reflectivity with the NSSL national reflectivity mosaic at 5-minute intervals and graphical displays of a large array of 2-D fields and ensemble products, including postage stamps and probability maps

Over 1000 CPUs at the Pittsburgh Supercomputing Center (PSC) will be used to produce the forecasts while additional processors at the University of Oklahoma Supercomputing Center for Education and Research (OSCER) will be used for post-processing. A special super-high-speed link capable of 200 MB/s will be set up between PSC and OSCER for data transfer.

Results of realtime forecasts and preliminary retrospective analysis on selected cases will be presented at the conference.

Available online at http://ams.confex.com/ams/pdfpapers/124587.pdf.

Xue, M., F. Kong, K. W. Thomas, J. Gao, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. C. Coniglio, J. Du, 2009: CAPS realtime 4 km multi-model convection-allowing ensemble and 1 km convection-resolving forecasts for the NOAA Hazardous Weather Testbed 2009 Spring Experiment. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Omaha, NE, USA, Amer. Meteor. Soc., CD-ROM, 16A.2.

Available online at http://ams.confex.com/ams/23WAF19NWP/techprogram/paper_154323.htm.

Xue, M., F. Kong, K. W. Thomas, J. Gao, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. C. Coniglio, J. Du, 2008: CAPS realtime storm-scale ensemble and high-resolution forecasts as part of the NOAA Hazardous Weather Testbed 2008 Spring Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 12.2.

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142036.htm.

Yang, H., J. Zhang, C. Langston, 2009: Synchronization of Radar Observations with Multi-Scale Storm Tracking. Advances in Atmospheric Sciences, 26, 78-86.

Yeary, M. B., B. McGuire, D. Forsyth, W. Benner, G. Torok, 2007: Target tracking at the National Weather Radar Testbed: a progress report on detecting and tracking aircraft.. Preprints, The 23rd Conference on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, USA, American Meteorology Society, CD-ROM, 8A.1.

Yeary, M., R. Palmer, M. Xue, T. Y. Yu, G. Zhang, A. Zahrai, J. Crain, Y. Zhang, R. Doviak, Q. Xu, P. Chilson, 2008: Introduction to multi-channel receiver development for the realization of multi-mission capabilities at the National Weather Radar Testbed. Extended Abstracts, 24rd Conference on Interactive Information Processing Systems (IIPS), New Orleans, LA, USA, AMS, 9A.3.

Yeary, M., G. E. Crain, A. Zahrai, T. Yu, R. Palmer, G. Zhang, Y. Zhang, R. J. Doviak, P. Chilson, M. Xue, Q. Xu, 2009: An update on multi-channel receiver development for the realization multi-mission capabilities at the national weather radar testbed. Extended Abstracts, 25th Conference on International Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Phoenix, AZ, USA, AMS, CD-ROM, 8B.5.

Yeary, M., J. Crain, A. Zahrai, R. Kelley, J. Meier, Y. Zhang, I. Ivic, C. Curtis, R. Palmer, T. Y. Yu, G. Zhang, R. J. Doviak, P. B. Chilson, M. Xue, Q. Xu, 2010: A status report on the RF and digital components of the multi-channel receiver development at the National Weather Radar Testbed. Extended Abstracts, 26th Conference on International Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, Atlanta, GA, USA, AMS, CD-ROM, 14B.3.

Available online at http://ams.confex.com/ams/90annual/techprogram/paper_160298.htm.

Yeary, M., G. Crain, R. Kelley, J. Meier, Y. Zhang, R. Palmer, T. Yu, A. Zahrai, I. Ivic, C. Curtis, R. Doviak, 2011: Phased Array Weather / Multipurpose Radar. IEEE Aerospace and Electronic Systems Magazine, 26, 12-15.

The first phased array radar dedicated to weather observation and analysis is now instrumented with eight simultaneous digital receivers. The addition of these additional channels will enable the use of advanced signal processing to improve signal/clutter in an adaptive mode. Elimination of strone point and ground clutter returns from the low-level, volumetrically-distributed weather cell returns is a new application of adaptive processing. The NSF funded 8-channel receiver has been added to the National Weather Radar Testbed (NWRT) system in Norman, Oklahoma, to enable operation as a multi-function and/or adaptive processing system. Herein, we describe the system concept, system installation and early results from fielded weather data returns.

Available online at http://pubget.com/paper/pgtmp_af0880c191fac8cb0219d9949a889cec.

Yeary, M., G. Crain, A. Zahrai, R. Kelley, J. Meier, Y. Zhang, I. Ivic, C. Curtis, R. Palmer, T. Y. Yu, R. Doviak, 2011: An update on the multi-channel phased array Weather Radar at the National Weather Radar Testbed. Extended Abstracts, Radar Conference (RADAR), 2011 IEEE, Kansas City, MO, USA, IEEE, 971-973.

The first phased array radar dedicated to weather observation and analysis is now instrumented with eight, simultaneous digital receivers. The multi-channel receiver will collect signals from the sum, azimuth-difference, elevation difference, and five broad-beamed auxiliary channels. The multi-channel receiver will allow the direct implementation of interferometry techniques to estimate crossbeam wind, shear and turbulence within a radar resolution volume. Access to the auxiliary channels will enable clutter mitigation and advanced array processing for high data quality with short dwell times. Potential benefits of high quality and high resolution data together with angular shear and turbulence include better understanding of storm dynamics and convective initiation, as well as better detection of small-scale phenomena including tornado and microbursts, ultimately leading to increased lead time for warnings, and improved weather prediction. This paper will describe the system concept, system installation and early results from fielded weather data returns.

Available online at http://ieeexplore.ieee.org/xpls/abs_all.jsp?tp=&arnumber=5960680.

Yong, B., L. Ren, Y. Hong, J. Wang, J. Gourley, S. Jiang, X. Chen, W. Wang, 2010: Hydrologic evaluation of Multisatellite Precipitation Analysis standard precipitation products in basins beyond its inclined latitude band: A case study in Laohahe Basin, China. Water Resources Research, 46, .

Yong, B., L. Ren, Y. Hong, J. Gourley, X. Chen, Y. Zhang, X. Yang, Z. Zhang, W. Wang, 2011: A novel multiple flow direction algorithm for computing the topographic wetness index. Hydrology Research, 43, 135-145.

The topographic wetness index (TWI), frequently used in approximately characterizing the spatial distribution of soil moisture and surface saturation within a watershed, has been widely applied in topography-related geographical processes and hydrological models. However, it is still questionable whether the current algorithms of TWI can adequately model the spatial distribution of topographic characteristics. Based upon the widely-used multiple flow direction approach (MFD), a novel MFD algorithm (NMFD) is proposed for improving the TWI derivation using a Digital Elevation Model (DEM) in this study. Compared with MFD, NMFD improves the mathematical equations of the contributing area and more precisely calculates the effective contour length. Additionally, a varying exponent strategy is adopted to dynamically determine the downslope flow-partition exponent. Finally, a flow-direction tracking method is employed to address grid cells in flat terrain. The NMFD algorithm is first applied to a catchment located upstream of the Hanjiang River in China to demonstrate its accuracy and improvements. Then NMFD is quantitatively evaluated by using four types of artificial mathematical surfaces. The results indicate that the error generated by NMFD is generally lower than that computed by MFD, and NMFD is able to more accurately represent the hydrological similarity of watersheds.

You, T., Y. Wang, A. Shapiro, M. B. Yeary, D. S. Zrnic, 2007: Characterization of Tornado Spectral Signatures Using Higher-Order Statistics. Journal of Atmospheric and Oceanic Technology, 24, 1997-2013.

Yu, T. Y., A. B. Chalamalasetti, R. J. Doviak, D. S. Zrnic, 2006: Resolution Enhancement Technique using Range Oversampling. Journal of Atmospheric and Oceanic Technology, 23, 228-240.

Yu, T. Y., G. Zhang, A. Chalamalasetti, R. J. Doviak, D. S. Zrnic, 2005: Improve Radar Resolution using Range Oversampling. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, 4R.4.

YU, T. Y., M. B. Orescanin, C. D. Curtis, D. S. Zrnic, D. E. Forsyth, 2007: Beam Multiplexing Using the Phased-Array Weather Radar.. Journal of Atmospheric and Oceanic Technology, 24, .

Yu, T. Y., M. B. Orescanin, C. D. Curtis, D. S. Zrnic, D. E. Forsyth, 2007: Optimization of weather update time and data quality using phased-array radar. Preprints, The 23rd Conference on Interactive Information Processing System (IIPS) for Meteorology, Oceanograph, and Hydrology, San Antonio, TX, USA, American Meteorological Society, CD-ROM, 7.6.

Yu, T. Y., Y. Wang, A. Shapiro, M. B. Yeary, D. S. Zrnic, R. J. Doviak, 2007: Characterization of Tornado Spectral Signatures using Higher-Order Spectra. Journal of Atmospheric and Oceanic Technology, 24, .

Yu, T., S. Torres, R. Reinoso-Rondinel, D. Vigouroux-Cavolina, 2011: Maximizing the benefits of adaptive scanning for weather radars: the development of an adaptive weather sensing framework to investigate the effectiveness of task-specific update time assignments. Extended Abstracts, 35th Conf. on Radar Meteor., Pittsburgh, PA, USA, Amer. Meteor. Soc., CD-ROM, 174.

A phased-array radar (PAR) can dynamically control beam position on a pulse-by-pulse basis, which allows a single radar to perform multiple functions without the limitations of mechanically scanned antennas. In this work, we exploit the PAR's multifunction capability for weather sensing, through which tracking of multiple storms and weather surveillance can be carried out independently and adaptively, as a means for better characterization and forecasting of storms of interest. A closed-loop framework for adaptive weather sensing is proposed; it consists of four components: storm identification, storm tracking, task management, and task scheduling. To dynamically schedule multiple competing tasks, the time balance method, which was originally developed for military applications and recently applied to weather observations, is employed. In this work, reflectivity fields observed by operational WSR-88D radars are used to simulate high-temporal-resolution PAR observations in order to demonstrate the feasibility of the proposed framework. With these simulations, we can demonstrate that a multifunction PAR can adaptively scan a number of regions of interest (storm cells) with task-specific update times. This can be accomplished with no degradation in data quality and higher-temporal resolution compared to conventional radar, while surveillance is maintained to ensure the tracking of developed storms and the detection of new formations. However, the performance of adaptive weather sensing depends on the requested update time for each task. Hence, simple and intuitive rules for the assignment of update times were developed. In addition, optimal update times were estimated by solving a constrained optimization problem. The performance of the two approaches was statistically evaluated and will be shown and discussed during the presentation.

Zhang, P., A. Ryzhkov, D. Zrnic, 2006: Polarimetric prototype of the WSR-88D radar observations of insects and birds. Preprints, 12th Conference on Aviation, Range, and Aerospace Meteorology, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P6.4.

Zhang, P., S. Liu, Q. Xu, Lulin Song, 2005: Storm targeted radar wind retrieval system. 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, P8R1.

Zhang, G., T-Y Yu, R. J. Doviak, 2005: Angular and range interferometry to refine weather radar resolution. Radio Science, 39, .

Zhang, J., K. Howard, J. J. Gourley, 2005: Constructing three-dimensional multiple radar reflectivity mosaics: examples of convective storms and stratiform rain echoes. Journal of Atmospheric and Oceanic Technology, 22, 30-42.

Zhang, P., S. Liu, Q. Xu, 2005: Quality control of Doppler velocities contaminated by migrating birds. Part I: Feature extraction and quality control parameters. Journal of Atmospheric and Oceanic Technology, 22, 1105-1113.

Zhang, S. W., C. J. Qiu, Q. Xu, 2005: Reply. Journal of Applied Meteorology, 44, 551-552.

Zhang, P., A. Ryzhkov, D. Zrnic, 2005: Observations of insects and birds with a polarimetric prototype of the WSR-88D radar. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, American Meteorological Society, CD-ROM, 9R.6.

Zhang, J., S. Wang, 2006: An Automated 2D Multipass Doppler Radar Volocity Dealiasing Scheme. Journal of Atmospheric and Oceanic Technology, 23, 1239-1248.

Zhang, G., R. J. Doviak, 2007: Spaced-Antenna Interferometry to Measure Crossbeam Wind, Shear, and Turbulence: Theory and Formulation.. Journal of Atmospheric and Oceanic Technology, 24, 791-805.

The theory of measuring crossbeam wind, shear, and turbulence within the radar's resolution volume V6 is described. Weather radar interferometry is formulated for such measurements using phased-array weather-radar. The formulation for a Spaced Antenna Interferometer (SAI) includes shear of the mean wind, allows turbulence to be anisotropic, and allows receiving beams to have elliptical cross sections. Auto- and cross-correlation functions are derived based on wave scattering by randomly distributed particles. Antenna separation, mean wind, shear, and turbulence all contribute to signal de-correlation. Crossbeam wind cannot be separated from shear and thus crossbeam wind measurements are biased by shear. It is shown that SAI measures an apparent crossbeam wind (i.e., the angular shear of the radial wind component). Whereas angular shear and turbulence within V6 cannot be separated using monostatic Doppler techniques, they can be separated using the SAI.

Zhang, G., R. J. Doviak, R. Palmer, T. Y. Yu, P. Chilson, 2005: Bistatic Interferometry to Measure Clear Air Wind. Preprints, 32nd Conference on Radar Meteorology, Albuquerque, NM, USA, AMS, CD-ROM, P2R.11.

Zhang, G., R. J. Doviak, X. Chen, 2007: Space Antenna Interferometry to Detect Discrete Objects and Sub-Volume Inhomogeneities of Reflectivity. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, 8B1.

Zhang, P., A. Ryzhkov, D. Zrnic, 2007: Kelvin-Helmholtz Waves Observed by a Polarimetric Prototype of the WSR-88D Radar. Extended Abstracts, 33rd International Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P10.4. [Available from Pengfei Zhang, National Weather Center, 120 David L. Boren Blvd. Suite 4502, Norman, OK, USA, 73072.]

At 15:40UTC on 2 May 2005, wave-like bright band is observed at 0.5o elevation angle by KOUN radar. The band highlighted by stronger reflectivity (~30dBZ), high Zdr (~2dB) and low hv (~0.9) moves eastwardly and last about 1 hour in KOUN radar scope. Doppler velocity observation shows strong wind shear in vertical direction at about 2 km height. Rawinsonde of OUN station at 12 UTC observes wind shift from NE (40o) at 1.2 km height to SW (220o) at 2.1 km height. Sounding also shows atmosphere is stable in the whole troposphere. 0oC temperatures layer locates at 2.1 km. Temperature is higher than 0oC underneath it. It means bright band is right embedded in the wind shear layer. Thus, we believe that bright band is altered by Kelvin-Helmholtz wave.

Zhang, G., Q. Cao, M. Xue, P. Chilson, M. Morris, R. Palmer, J. Brotzke, T. Schuur, E. Brandes, K. Ikeda, A. Ryzhkov, D. Zrnic, E. Jessup, 2008: A field experiment to study rain microphysics using video disdrometers and polarimetric S and X-band radars. Preprints, Symposium on Recent Developments in Atmospheric Applications of Radar and Lidar, New Orleans, LA, USA, American Meteorological Society, P2.23.

Zhang, J., K. Howard, X. Xu, 2008: A warm season radar QPE algorithm using adaptive Z-R relationships. Proc. World Environmental and Water Resources Congress 2008, Honolulu, HI, USA, Amer. Soc. Civil Engineers, CD-ROM, 420.pdf.

Zhang, J., C. Langston, K. Howard, 2008: Three-dimensional radar mosaic integrating WSR-88Ds and Canadian radar network. Preprints, The 13th Conf. on Aviation, Range, and Aerospace Meteorology, New Orleans, LA, USA, Amer. Meteor. Soc., CD-ROM, P4.4.

Zhang, J., C. Langston, K. Howard, 2007: Brightband identification from vertical profile of reflectivity. Preprints, The 33rd International Conf. on Radar Meteorology, Cairns, Australia, Amer. Meteor. Soc., P8A.13.

Zhang, J., C. Langston, K. Howard, 2006: Vertical profiles of reflectivity for different precipitation regimes. Proc. The 4th European Conference on Radar in Meteorology and Hydrology, Barcelona, Spain, Servei Meteorologic de Catalunya, 225-228.

Zhang, J., K. Howard, S. Wang, 2006: Single radar Cartesian grid and adaptive radar mosaic system. Preprints, The 12th Conference on Aviation, Range, and Aerospace Meteorolog, Atlanta, GA, USA, Amer. Meteor. Soc., 1.8.

Zhang, J., C. Langston, K. Howard, B. Clarke, 2006: Gap-filling in 3D radar mosaic analysis using vertical profile of reflectivity. Preprints, The 12th Conference on Aviation, Range, and Aerospace Meteorology, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, P1.9.

Zhang, J., C. Langston, K. Howard, 2008: Bright Band Identification Based On Vertical Profiles of Reflectivity from the WSR-88D. Journal of Atmospheric and Oceanic Technology, 25, 1859-1872.

Zhang, J., K. Howard, P. L. Chang, P. T. Chiu, C. R. Chen, C. Langston, W. Xia, B. Kaney, P. F. Lin, 2008: High-Resolution QPE System for Taiwan. Data Assimilation for Atmospheric, Oceanic, and Hydrologic Applications, S. K. Park, L. Xu, Ed(s)., Springer-Verlag, 145-160.

Zhang, G., R. J. Doviak, 2008: Spaced-Antenna Interferometry to Detect and Locate Sub-Volume Inhomogeneities of Reflectivity: An Analogy with Monopulse Radar. Journal of Atmospheric and Oceanic Technology, 11, 1921-1938.

The theory of Spaced-Antenna Interferometry (SAI) is formulated to detect and locate deterministic objects and reflectivity inhomogeneities embedded within the phased-array weather radar’s resolution volume, V6, and to improve weather radar performance. An analogy is made between monopulse tracking and SAI. The cross-correlation function and its power spectrum are derived based on wave scattering by a large deterministic object and clusters of randomly distributed precipitation particles. It is shown that non uniform beam-filling leads to an effective narrower beam and an increase in cross-correlation coefficient at zero lag. Hence, an individual object or a sub-volume inhomogeneity can be detected and located by SAI. This capability further enhances the potential applications of phased-array weather radar used as a multi-mission system.

Zhang, G., Y. Li, R. J. Doviak, J. Carter, 2009: Multi-beam experiments for the phased array radar calibration and sidelobe reduction. Extended Abstracts, USNC-URSI 2009 NRSM, Boulder, CO, USA, United States National Committee (USNC)of the International Radi, 1-1.

The NWRT/PAR dual-scan (mechanical and electrical) capability is a unique feature, allowing concurrent multi-beam measurements (i.e., with boresight and squinted beams). As these beams are mechanically scanned, echoes received through sidelobes are not as coherent as the echoes received through the respective mainlobes because sidelobe amplitude and phase patterns for these beams differ. Thus, by jointly processing the data recorded for various squinted beams (corresponding to different antenna patterns), we suggest that we can distinguish echoes received through the main and sidelobes.

In this study, we formulate the radar equation for PAR calibration and conduct multi-beam experiments. The PAR beam electronically points to five directions uniformly spaced or optimally chosen while mechanically scanning the antenna. Hence, five sets of radar data are collected with one mechanical scan, and then jointly processed. By calculating the standard deviation of the multi-beam measurements, the echoes contaminated by clutter through sidelobes are identified and filtered out. It is found that the multi-beam technique can reduce sidelobe contamination of not only ground clutter but also that of moving targets such as aircrafts. It is also shown that the experiment with optimally chosen beam directions is more effective in reducing the sidelobe effects than that of uniformly spaced beams.

Zhang, G., R. J. Doviak, C. Curtis, Q. Cao, 2008: Multi-pattern measurements for calibration and sidelobe reduction on the National Weather Radar Testbed.. Extended Abstracts, AMS 88th Annual Conference, New Orleans, LA, USA, AMS, P1.12.

Zhang, J., K. Howard, S. Vasiloff, C. Langston, B. Kaney, A. Arthur, S. Van Cooten, K. Kelleher, D. Kitzmiller, F. Ding, D. J. Seo, M. Mullusky, E. Wells, T. Schneider, C. Dempsey, 2009: National Mosaic and multi-sensor QPE (NMQ) system: description, results and future plans. Preprints, The 34th Conference on Radar meteorology, Williamsburg, VA, USA, American Meteorological Society, 7A.1.

Zhang, J., Y. Qi, 2009: Correction of bright band effects in radar observations from plain areas. Preprints, The 34th Conf. on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, P14.5.

Zhang, P., V. Melnikov, D. Zrnic, A. Ryzhkov, 2009: Recombination of dual-polarization super resolution level II data. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P13.18.

In this paper, a functional description of how to recombine super resolution (0.5 deg) polarimetric level II data into regular (legacy 1 deg) resolution is presented. Then test of classification algorithm on these data has been made. The test results demonstrate that it is essentially not affected by the recombination procedure. This is because there is no substantial difference between polarimetric data computed in the super resolution and legacy modes. Nonetheless, testing was done on one data set hence it is premature to accept this finding in general. Additional testing should be made on a variety of weather radar data.

Zhang, P., P. Chan, R. Doviak, M. Fang, 2009: Estimate of Eddy Dissipation Rates Using Spectrum Width Observed by Hong Kong TDWR Radar. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P6.9.

The relationship between Doppler spectrum width and atmospheric turbulence has been established for decades. Based on it, an algorithm that can estimate Eddy Dissipation Rates (EDR) from measured spectrum width has been developed. In the algorithm wind shear contributions are considered and removed from measured spectrum width in order to accurately estimate pure atmospheric turbulence for aviation applications. Applying the algorithm on the spectrum width data observed by Hong Kong TDWR radar over the airport, we have successfully estimated and categorized EDR in different weather environments such as Typhoon and thunderstorms. The EDRs derived from TDWR measured spectrum width have also been compared with relevant aircraft measured EDRs. The results are discussed and presented in the paper.

Zhang, P., M. Zhu, 2009: Radar Image Segmentation Using Active Contour Method. Preprints, 34th Conference on Radar Meteorology, Williamsburg, VA, USA, AMS, CD-ROM, P9.2.

Recently, active contour method has been widely applied on image processing in seeking the edges or contours of desired features. Active contour is the procedure to deform an initial given curve so that a designed functional of the curve will reach a local minimum. We introduce a new energy functional that involves the maximal intensity of image and a flexible parameter. By minimizing such energy functional and optimizing the parameter in the functional, the edge of desired feature can be found. This method has been applied on weather radar reflectivity fields to segment weather echoes from clear air echoes.

Zhang, G., R. J. Doviak, D. Zrnic, J. Crain, D. Stainman, Y. Al-Rashid, 2009: Phased Array Radar Polarimetry for Weather Sensing: A Theoretical Formulation for Bias Corrections. IEEE Transactions on Geoscience and Remote Sensing, 47, 3679-3689.

It is becoming widely accepted that radar polarimetry provides accurate and informative weather measurements, while phased array technology can shorten data updating time. In this paper, a theory of phased array radar polarimetry is developed to establish the relation between electric fields at the antenna of phased array radar and the fields in a resolution volume filled with hydrometeors. It is shown that polarimetric measurements with an electronically steered beam can cause measurement biases that are comparable to or even larger than the intrinsic polarimetric characteristics of hydrometeors. However, these biases are correctable if the transmitted electric fields are known. A correction to the measured scattering matrix is derived that removes biases in meteorological variables. The challenges and opportunities for weather sensing with polarimetric phased array radar are discussed.

Zhang, J., Y. Qi, 2010: A real-time algorithm for the correction of bright band effects in radar-derived precipitation estimation. J. Hydrometeorology, 11, 1157-1171.

The bright band (BB) is a layer of enhanced reflectivity due to melting of aggregated snow and ice crystals.
The locally high reflectivity causes significant overestimation in radar precipitation estimates if an appropriate
correction is not applied. The main objective of the current study is to develop a method that automatically
corrects for large errors due to BB effects in a real-time national radar quantitative precipitation estimation
(QPE) product. An approach that combines the mean apparent vertical profile of reflectivity (VPR) computed
from a volume scan of radar reflectivity observations and an idealized linear VPR model was used for
computational efficiency. The methodology was tested for eight events from different regions and seasons in
the United States. The VPR correction was found to be effective and robust in reducing overestimation errors
in radar-derived QPE, and the corrected radar precipitation fields showed physically continuous distributions.
The correction worked consistently well for radars in flat land regions because of the relatively uniform spatial
distributions of the BB in those areas. For radars in mountainous regions, the performance of the correction is
mixed because of limited radar visibility in addition to large spatial variations of the vertical precipitation
structure due to underlying topography.

Zhang, J., Y. Qi, D. Kingsmill, K. Howard, 2010: Radar-based quantitative precipitation estimation for the cool season in northern California: case studies from the NOAA Hydrometeorological Testbed (HMT).. Proc. The World Environmental and Water Resources Congress 2010, Providence, RI, USA, Amer. Soc. Civil Engineers, 4639-4647.

The Hydrometeorological Testbed (HMT; http://hmt.noaa.gov) of the National Oceanic and Atmospheric Administration (NOAA) is a demonstration project intended to accelerate the infusion of new technologies, models, and scientific results from the research community into daily forecasting operations of the National Weather Service (NWS) and its River Forecast Centers (RFCs). The project focuses on the development and use of hydrometeorological instrumentation and models to aid forecasters, hydrologists and water resource managers in their decision-making process. The HMT plan calls for a sequence of regional demonstrations in vitally important watersheds in different parts of the United States. The first demonstration in the sequence (HMT-West) began in December 2005 in northern California’s American River Basin above Sacramento (Fig.1). This presentation focuses on one of the critical aspects of HMT: quantitative precipitation estimation (QPE). Two cases to be discussed occurred over the periods 30 December 2005 to 1 January 2006, and 13 to 15 January 2006. Scanning radar data were collected from several 10-cm National Weather Service (NWS) WSR-88D (Weather Surveillance Radar – 1988 Doppler) radars, one 3-cm polarimetric Doppler radar and one 5-cm mobile Doppler radar. The current study is focused on generating radar-based QPE from the WSR-88Ds for the two events. The impact of vertical profile of reflectivity (VPR) on radar-derived QPE in the complex terrain of northern California was analyzed and a variety of radar QPE techniques were applied to improve the precipitation estimates. Rain gauge observations after careful quality control were used to assess the accuracy of various radar precipitation estimates.

Zhang, G., R. J. Doviak, D. S. Zrnic, R. Palmer, L. Lei, 2011: Polarimetric Phased Array Radar for Weather Measurement: A Planar or Cylindrical Configuration?. Journal of Atmospheric and Oceanic Technology, 28, 63-73.

This paper suggests a cylindrical configuration for agile beam polarimetric phased-array radar (PPAR) for weather surveillance. The most often used array configuration for PAR is a planar array antenna. The planar configuration, however, has significant deficiencies for polarimetric measurements, as well as other limitations, such as increases in beamwidth, decreases of sensitivity, and changes in the polarization basis when the beam scans off its broadside. The cylindrical polarimetric phased-array radar (CPPAR) is proposed to avoid
these deficiencies. The CPPAR principle and potential performance are demonstrated through theoretical analysis and simulation. It is shown that the CPPAR has the advantage of a scan-invariant polarization basis, and thus avoids the inherent limitations of the planar PPAR (i.e., PPPAR).

Zhang, G., S. Luchs, A. Ryzhkov, M. Xue, L. Ryzhkova, Q. Cao, 2011: Winter precipitation microphysics characterized by polarimetric radar and video disdrometer observations in central Oklahoma. Journal of Applied Meteorology and Climatology, 50, 1558-1570.

The study of precipitation in different phases is important to understanding the physical processes that occur in storms, as well as to improving their representation in numerical weather prediction models. A 2D video disdrometer was deployed about 30 km from a polarimetric weather radar in Norman, Oklahoma, (KOUN) to observe winter precipitation events during the 2006/07 winter season. These events contained periods of rain, snow, and mixed-phase precipitation. Five-minute particle size distributions were generated from the disdrometer data and fitted to a gamma distribution; polarimetric radar variables were also calculated for comparison with KOUN data. It is found that snow density adjustment improves the comparison substantially, indicating the importance of accounting for the density variability in representing model microphysics.

Zhang, G., R. J. Doviak, D. Priegnitz, J. Carter, C. D. Curtis, 2011: Multipatterns of the National Weather Radar Testbed Mitigate Clutter Received via Sidelobes. Journal of Atmospheric and Oceanic Technology, 28, 401-409.

The Phased Array Radar (PAR) of the National Weather Radar Testbed (NWRT) has a unique hybrid (mechanical and electrical) azimuth scan capability, allowing weather observations with different antenna patterns. Observations show the standard deviation of the sample mean power of weather echoes received through the main lobe of a set of squinted beams is less than clutter received via sidelobes. This then allows use of a multi-pattern technique to cancel sidelobe echoes from moving scatterers, echoes that cannot be filtered with a ground-clutter canceller. Although the multi-pattern technique was developed to cancel clutter received through sidelobes, results show clutter from objects moving within the beam can also be canceled.

Zhang, P., D. Zrnic, A. Ryzhkov, 2011: Partial Beam Blockage Correction Using Dual-Polarimetric Measuremments. Extended Abstracts, 35th Conference on Radar Meteorology, Pittsburgh, PA, USA, American Meteorological Society, 15A.4.

A new method for mitigation of partial beam blockage that uses the consistency between reflectivity factor Z and specific differential phase Kdp and their radial integrals in rain is presented. The immunity of differential phase DP to partial beam blockage is utilized to estimate the bias of reflectivity factor caused by beam blockage. The algorithm is tested on dual-polarization radar data collected by the NCAR SPOL radar during the SoWMEX/TiMREX experiment in June 2008 in Taiwan. Corrected reflectivity factors in the blocked sectors are compared with corresponding values deduced from a digital elevation map (DEM) to show the advantage of the suggested method in areas where obstacles such as high-rising buildings cause additional blockage which is not accounted for by DEM. The accuracy and robustness of the method is quantitatively evaluated using a series of radar volume scans obtained in three rainfall events.

Available online at http://ams.confex.com/ams/35Radar/webprogram/Paper190790.html.

Zhang, J., K. Howard, C. Langston, S. Vasiloff, B. Kaney, A. Arthur, S. Van Cooten, K. Kelleher, D. Kitzmiller, F. Ding, D. J. Seo, E. Wells, C. Dempsey, 2011: National Mosaic and Multi-sensor QPE (NMQ) System: Description, Results, and Future Plans. Bulletin of the American Meteorological Society, 92, 1321-1338.

The National Mosaic and Multi-sensor QPE (Quantitative Precipitation Estimation), or “NMQ”, system was initially developed from a joint initiative between the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory, the Federal Aviation Administration's Aviation Weather Research Program, and the Salt River Project. Further development has continued with additional support from the National Weather Service (NWS) Office of Hydrologic Development, the NWS Office of Climate, Water, and Weather Services, and the Central Weather Bureau of Taiwan. The objectives of NMQ research and development (R&D) are 1) to develop a hydrometeorological platform for assimilating different observational networks toward creating high spatial and temporal resolution multisensor QPEs for f lood warnings and water resource management and 2) to develop a seamless high-resolution national 3D grid of radar reflectivity for severe weather detection, data assimilation, numerical weather prediction model verification, and aviation product development.

Through about ten years of R&D, a real-time NMQ system has been implemented (http://nmq.ou.edu). Since June 2006, the system has been generating high-resolution 3D reflectivity mosaic grids (31 vertical levels) and a suite of severe weather and QPE products in real-time for the conterminous United States at a 1-km horizontal resolution and 2.5 minute update cycle. The experimental products are provided in real-time to end users ranging from government agencies, universities, research institutes, and the private sector and have been utilized in various meteorological, aviation, and hydrological applications. Further, a number of operational QPE products generated from different sensors (radar, gauge, satellite) and by human experts are ingested in the NMQ system and the experimental products are evaluated against the operational products as well as independent gauge observations in real time.

The NMQ is a fully automated system. It facilitates systematic evaluations and advances of hydrometeorological sciences and technologies in a real-time environment and serves as a test bed for rapid science-to-operation infusions. This paper describes scientific components of the NMQ system and presents initial evaluation results and future development plans of the system.

Zhu, W. H., D. M. Schultz, D. W. Kennedy, K. E. Kelleher, N. N. Soreide, 2007: The National Severe Storms Laboratory Historical Weather Data Archives data management and web access system. Bulletin of the American Meteorological Society, 87, 1679-1683.

Zhu, M., V. Lakshmanan, P. Zhang, Y. Hong, K. Cheng, S. Chen, 2011: Spatial verification using a true metric. Atmospheric Research, 102, 408-419.

Verifying high-resolution forecasts is challenging because forecasts can be considered
good by their end-users even when there is no pixel-to-pixel correspondence
between the forecast and the verification field. Many of the verification methods that
have been proposed to address the verification of high-resolution forecasts are based on
filtering, warping or searching within a neighborhood of pixels in the forecast and/or
the verification fields in order to retain the capability to use a simple metric. This is
because it is necessary for a verification score to be a metric to allow comparisons of
forecasts. In this paper, we devise a computationally simple scalar spatial verification
metric that is capable of ordering forecasts without preprocessing the fields. The metric
is based on the insight that in the verification problem, the observation field can be
considered a reference field that forecast fields are ordered against. This new metric is
demonstrated on synthetic and real model forecasts of precipitation.

Available online at http://cimms.ou.edu/~lakshman/Papers/verifmetric.pdf.

Ziegler, C. L., E. N. Rasmussen, M. S. Buban, Y. P. Richardson, L. J. Miller, R. M. Rabin, 2007: The "Triple Point" on 24 May 2002 during IHOP. Part II: Ground-Radar and In Situ Boundary Layer Analysis of Cumulus Development and Convection Initiation. Monthly Weather Review, 135, 2443-2472.

Cumulus formation and convection initiation are examined near a cold front–dryline “triple point” intersection on 24 May 2002 during the International H2O Project (IHOP). A new Lagrangian objective analysis technique assimilates in situ measurements using time-dependent Doppler-derived 3D wind fields, providing output 3D fields of water vapor mixing ratio, virtual potential temperature, and lifted condensation level (LCL) and water-saturated (i.e., cloud) volumes on a subdomain of the radar analysis grid. The radar and Lagrangian analyses reveal the presence of along-wind (i.e., longitudinal) and cross-wind (i.e., transverse) roll circulations in the boundary layer (BL). A remarkable finding of the evolving radar analyses is the apparent persistence of both transverse rolls and individual updraft, vertical vorticity, and reflectivity cores for periods of up to 30 min or more while moving approximately with the local BL wind. Satellite cloud images and single-camera ground photogrammetry imply that clouds tend to develop either over or on the downwind edge of BL updrafts, with a tendency for clouds to elongate and dissipate in the downwind direction relative to cloud layer winds due to weakening updrafts and mixing with drier overlying air. The Lagrangian and radar wind analyses support a parcel continuity principle for cumulus formation, which requires that rising moist air parcels achieve their LCL before moving laterally out of the updraft. Cumuli form within penetrative updrafts in the elevated residual layer (ERL) overlying the moist BL east of the triple point, but remain capped by a convection inhibition (CIN)-bearing layer above the ERL. Dropsonde data suggest the existence of a convergence line about 80 km east of the triple point where deep lifting of BL moisture and locally reduced CIN together support convection initiation.

Ziegler, C. L., E. N. Rasmussen, M. Buban, Y. Richardson, L. J. Miller, R. Rabin, 2005: The boundary layer cumulus formation process near a cold frontal-dryline intersection on 24 May 2002 during IHOP. Preprints, 11th Conference on Mesoscale Processes, Albuquerque, NM, USA, AMS, J6J.2.

Zink, M., D. Westbrook, S. Abdallah, B. Horling, V. Lakamraju, E. Lyons, V. Manfredi, J. Kurose, K. Hondl, 2005: Meteorological Command and Control: An End-to-end Architecture for a Hazardous Weather Detection Sensor Network. Extended Abstracts, Workshop on End-to-End, Sense-and-Respond Systems, Applications, and Services, Seattle, WA, USA, X, XX.

Zink, M., D. Westbrook, E. Lyons, K. Hondl, J. Kurose, F. Junyent, L. Krnan, V. Chandrasekar, 2005: NetRad: Distributed, Collaborative and Adaptive Sensing of the Atmosphere.. Proc. International Conference on Distributed Computing in Sensor Systems, Marina Del Rey, CA, USA, X, XX.

Zrnic, D., A. Zahrai, S. Torres, C. Curtis, I. Ivic, V. Melnikov, 2005: Development of advanced techniques using the NOAA's WSR-88D research radar. Preprints, 21st International Conference on Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Diego, CA, USA, American Meteorological Society, 5.9.

Zrnic, D. S., V. M. Melnikov, J. K. Carter, 2005: Calibrating Differential Reflectivity on the WSR-88D. Radar report 1, NOAA/NSSL, 34 pp. [Available from Dusan Zrnic, National Severe Storms Laboratory, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

A procedure on how to calibrate differential reflectivity on the WSR-88D is described. It has been tested on the NOAA's modified WSR-88D research and development polarimetric radar and is directly applicable to radars which simultaneously transmit and receive waves having horizontal and vertical polarizations.

Available online at http://www.cimms.ou.edu/~schuur/jpole/WSR-88D_reports.html.

Zrnic, D. S., V. M. Melnikov, J. K. Carter, 2006: Calibrating differential reflectivity on the WSR-88D. Journal of Atmospheric and Oceanic Technology, 23, 944-951.

A calibration procedure of differential reflectivity on the Weather Surveillance Radar-1988 Doppler (WSR-88D) is described. It has been tested on NOAA's modified WSR-88D research and development polarimetric radar and is directly applicable to radars that simultaneously transmit and receive waves having horizontal and vertical polarization.

Zrnic, D. S., V. M. Melnikov, A. V. Ryzhkov, 2006: Correlation coefficients between horizontally and vertically polarized returns from ground clutter. Journal of Atmospheric and Oceanic Technology, 23, 381-394.

Characteristics of the magnitude and phase of correlation coefficients between horizontally and vertically polarized returns from ground clutter echoes are quantified by analyzing histograms obtained with an 11-cm wavelength weather surveillance radar in Norman, Oklahoma. The radar receives simultaneously horizontal and vertical (SHV) electric fields and can transmit either horizontal fields or both vertical and horizontal fields. The differences between correlations obtained in this SHV mode and correlations measured in alternate H, V mode are reviewed; a histogram of differential phase obtained in Florida using alternate H, V mode is also presented. Data indicate that the backscatter differential phase of clutter has a broad histogram that completely overlaps the narrow histogram of precipitation echoes. This is important as it implies that a potent discriminator for separating clutter from meteorological echoes is the texture of the differential phase. Values of the copolar cross-correlation coefficient from clutter overlap completely those from precipitation, and effective discrimination is possible only if averages in range are taken. It is demonstrated that the total differential phase (system and backscatter) depends on the polarimetric measurement technique and the type of scatterers. In special circumstances, such as calibrating or monitoring the radar, clutter signal can be beneficial. Specifically, system differential phase can be estimated from histograms of ground clutter, receiver differential phase can be estimated from precipitation returns, and from these two, the differential phase of transmitted waves is easily computed.

Zrnic, D. S., V. M. Melnikov, 2007: Ground clutter recognition using polarimetric spectral parameters. Preprints, 33rd Conference on Radar Meteorology, Cairns, Australia, AMS, CD-ROM, P11B13.

Zrnic, D. S., J. F. Kimpel, D. F. Forsyth, A. Shapiro, G. Crain, R. Ferek, J. Heimmer, W. Benner, T. J. McNellis, 2007: Agile beam phased array radar for weather observations. Bulletin of the American Meteorological Society, 88, 1753-1766.

Zrnic, D. S., G. Zhang, V. Melnikov, J. Andric, 2010: Three-body scattering and hail size. Journal of Applied Meteorology and Climatology, 49, 687-700.

Three-body scattering signature is an appendage seen on weather radar displays of reflectivity behind strong storm cells. It is caused by multiple scattering between hydrometeors and ground. The radar equation for this phenomenon is reexamined and corrected to include the coherent wave component producing 3 dB more power than previously reported. Furthermore, the possibility to gauge hail size causing this phenomena is explored. A model of forward scattering by spherical hail and accepted values of ground backscattering cross sections is used in an attempt to reconcile the reflectivity in this signature with observations. This work demonstrates that the signature can be caused by small (<10 mm) to moderate (20 mm) size hail. A try to gauge hail size by comparing the direct return from hail with the three-body scattered return is made. The theory indicates fundamental ambiguities in size retrieval due to resonant effects. Although theory eliminates the number of hailstones per unit volume, the shape of hail size distribution and the cross section of ground contribute additional uncertainty to the retrieval.

Zrnic, D. S., G. Zhang, R. J. Doviak, 2011: Bias correction and Doppler measurement for polarimetric phased-array radar. IEEE Transactions on Geoscience and Remote Sensing, 49, 843-853.

This paper discusses ways to avoid and/or mitigate biases in polarimetric variables inherent to agile-beam planar phased-array radars. Two bias-avoiding schemes produce unbiased estimates of the polarimetric backscattering covariance matrix which are then combined into bias-free polarimetric variables. One concerns full polarimetric measurements and calls for adjusting the amplitudes and phases of the array elements so that the transmitted field equals that generated by a mechanically steered polarimetric weather radar antenna; this is followed by an additional adjustment of the received fields. The second scheme is also applicable to full polarimetric measurements but involves adjustments only of the received fields. Crucial to both schemes is decoupling of the Doppler effects from the terms of the covariance matrix. It is a significant part of the bias issue that had not been previously addressed. A scheme to reduce bias applicable to nondepolarizing media (i.e., diagonal backscattering matrix) is also addressed; it calls for multiplication of the fields received by each dipole as opposed to a combination of multiplication and addition required for full correction. The schemes are applied to the alternate transmission and simultaneous reception polarimetric mode and the simultaneous transmission and simultaneous reception mode.

Available online at http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5565444.

Zrnic, D. S., R. J. Doviak, G. Zhang, R. V. Ryzhkov, 2010: Bias in differential reflectivity due to cross-coupling through the radiation patterns of polarimetric weather radars. Journal of Atmospheric and Oceanic Technology, 49, 1624-1637.

Examined is bias in differential reflectivity and its effect on estimates of rain rate due to coupling of the vertically and horizontally polarized fields through the radiation patterns. To that end, a brief review of the effects of the bias on quantitative rainfall measurements is given. Suggestions for tolerable values of this bias are made. Of utmost interest is the bias produced by radars simultaneously transmitting horizontally and vertically polarized fields, as this configuration has been chosen for pending upgrades to the U.S. national network of radars (Weather Surveillance Radar-1988 Doppler; WSR-88D). The bias strongly depends on the cross-polar radiation pattern. Two patterns, documented in the literature, are considered.

Zrnic, D. S., 2012: Doppler radar for USA weather surveillance. Doppler Radar Observations - Weather Radar, Wind Profiler, Ionospheric Radar, and Other Advanced Applications, J. Bech, J. L. Chau, Ed(s)., InTech - Open Access Publisher http://www.intechopen.com, 3-32.

Weather radar had its beginnings at the end of Word War II when it was noticed that storms clutter radar displays meant to reveal enemy aircraft. Thus radar meteorology was born. Until the sixties only the return power from weather tracers was measured which offered the first glimpses into precipitation structure hidden inside clouds. Possibilities opened up to recognize hail storms, regions of tornadoes (i.e., hook echoes), the melting zone in stratiform precipitation, and even determine precipitation rates at the ground, albeit with considerable uncertainty. Technology innovations and discoveries made in government laboratories and universities were quickly adopted by the National Weather Service (NWS). Thus in 1957 the Miami Hurricane Forecast Center commissioned the first modern weather radar (WSR-57) the type subsequently installed across the continental United States. The radar operated in the 10 cm band of wavelengths and had beamwidth of about 2o. In 1974 more radars were added: the WSR-74S operating in the band of 10 cm wavelengths and WSR-74C in the 5 cm band. Development of Doppler radars followed, providing impressive experience to remotely observe internal motions in convective storms and infer precipitation amounts. Thus scientists quickly discovered tell tale signatures of kinematic phenomena (rotation, storm outflows, divergence) in the fields of radial velocities. After demonstrable successes with this technology the NWS commissioned a network of Doppler radars (WSR-88D=Weather Surveillance Radars, year 1988, Doppler), the last of which was installed in 1997. Much had happened since that time and the current status pertinent to Doppler measurements and future trends are discussed herein.